r47034 - Merge clarity-sshtransport-8237: Improve clarity of types in twisted.conch.ssh.transport

hawkowl-TA+aISz0psMTMxyoc4vAAJOcrHinNvQL0E9HWUfgJXw@public.gmane.org Sun, 20 Mar 2016 19:04:31 -0600 (MDT)
Newsgroups gmane.comp.python.twisted.commits
Message-ID <[email protected]>
Author: hawkowl
Date: Sun Mar 20 19:04:25 2016
New Revision: 47034

Added:
   trunk/twisted/conch/topfiles/8237.misc
Modified:
   trunk/twisted/conch/ssh/transport.py
   trunk/twisted/conch/test/test_transport.py

Log:
Merge clarity-sshtransport-8237: Improve clarity of types in twisted.conch.ssh.transport

Author: hawkowl
Reviewer: lukasa
Fixes: #8237

Modified: trunk/twisted/conch/ssh/transport.py
==============================================================================
--- trunk/twisted/conch/ssh/transport.py	(original)
+++ trunk/twisted/conch/ssh/transport.py	Sun Mar 20 19:04:25 2016
@@ -10,11 +10,14 @@
 Maintainer: Paul Swartz
 """
 
+from __future__ import absolute_import, division
+
+import binascii
+import hmac
 import struct
 import zlib
+
 from hashlib import md5, sha1, sha256, sha512
-import string
-import hmac
 
 from cryptography.exceptions import UnsupportedAlgorithm
 from cryptography.hazmat.backends import default_backend
@@ -23,7 +26,6 @@
 from twisted.internet import protocol, defer
 from twisted.python import log, randbytes
 
-
 from twisted.conch.ssh import address, keys, _kex
 from twisted.conch.ssh.common import (
     NS, getNS, MP, getMP, _MPpow, ffs, int_from_bytes
@@ -48,7 +50,7 @@
     """
     if bits % 8:
         raise ValueError("bits (%d) must be a multiple of 8" % (bits,))
-    return int_from_bytes(random(bits / 8), 'big')
+    return int_from_bytes(random(bits // 8), 'big')
 
 
 
@@ -122,26 +124,26 @@
     """
 
     cipherMap = {
-        '3des-cbc': (algorithms.TripleDES, 24, modes.CBC),
-        'blowfish-cbc': (algorithms.Blowfish, 16, modes.CBC),
-        'aes256-cbc': (algorithms.AES, 32, modes.CBC),
-        'aes192-cbc': (algorithms.AES, 24, modes.CBC),
-        'aes128-cbc': (algorithms.AES, 16, modes.CBC),
-        'cast128-cbc': (algorithms.CAST5, 16, modes.CBC),
-        'aes128-ctr': (algorithms.AES, 16, modes.CTR),
-        'aes192-ctr': (algorithms.AES, 24, modes.CTR),
-        'aes256-ctr': (algorithms.AES, 32, modes.CTR),
-        '3des-ctr': (algorithms.TripleDES, 24, modes.CTR),
-        'blowfish-ctr': (algorithms.Blowfish, 16, modes.CTR),
-        'cast128-ctr': (algorithms.CAST5, 16, modes.CTR),
-        'none': (None, 0, modes.CBC),
+        b'3des-cbc': (algorithms.TripleDES, 24, modes.CBC),
+        b'blowfish-cbc': (algorithms.Blowfish, 16, modes.CBC),
+        b'aes256-cbc': (algorithms.AES, 32, modes.CBC),
+        b'aes192-cbc': (algorithms.AES, 24, modes.CBC),
+        b'aes128-cbc': (algorithms.AES, 16, modes.CBC),
+        b'cast128-cbc': (algorithms.CAST5, 16, modes.CBC),
+        b'aes128-ctr': (algorithms.AES, 16, modes.CTR),
+        b'aes192-ctr': (algorithms.AES, 24, modes.CTR),
+        b'aes256-ctr': (algorithms.AES, 32, modes.CTR),
+        b'3des-ctr': (algorithms.TripleDES, 24, modes.CTR),
+        b'blowfish-ctr': (algorithms.Blowfish, 16, modes.CTR),
+        b'cast128-ctr': (algorithms.CAST5, 16, modes.CTR),
+        b'none': (None, 0, modes.CBC),
     }
     macMap = {
-        'hmac-sha2-512': sha512,
-        'hmac-sha2-256': sha256,
-        'hmac-sha1': sha1,
-        'hmac-md5': md5,
-        'none': None
+        b'hmac-sha2-512': sha512,
+        b'hmac-sha2-256': sha256,
+        b'hmac-sha1': sha1,
+        b'hmac-md5': md5,
+        b'none': None
      }
 
 
@@ -153,8 +155,8 @@
         self.encBlockSize = 0
         self.decBlockSize = 0
         self.verifyDigestSize = 0
-        self.outMAC = (None, '', '', 0)
-        self.inMAC = (None, '', '', 0)
+        self.outMAC = (None, b'', b'', 0)
+        self.inMAC = (None, b'', b'', 0)
 
 
     def setKeys(self, outIV, outKey, inIV, inKey, outInteg, inInteg):
@@ -218,7 +220,7 @@
         """
         mod = self.macMap[mac]
         if not mod:
-            return (None, '', '', 0)
+            return (None, b'', b'', 0)
 
         # With stdlib we can only get attributes fron an instantiated object.
         hashObject = mod()
@@ -228,9 +230,9 @@
         # Truncation here appears to contravene RFC 2104, section 2.  However,
         # implementing the hashing behavior prescribed by the RFC breaks
         # interoperability with OpenSSH (at least version 5.5p1).
-        key = key[:digestSize] + ('\x00' * (blockSize - digestSize))
-        i = string.translate(key, hmac.trans_36)
-        o = string.translate(key, hmac.trans_5C)
+        key = key[:digestSize] + (b'\x00' * (blockSize - digestSize))
+        i = key.translate(hmac.trans_36)
+        o = key.translate(hmac.trans_5C)
         result = _MACParams((mod, i, o, digestSize))
         result.key = key
         return result
@@ -277,7 +279,7 @@
         @return: The serialized MAC.
         """
         if not self.outMAC[0]:
-            return ''
+            return b''
         data = struct.pack('>L', seqid) + data
         return hmac.HMAC(self.outMAC.key, data, self.outMAC[0]).digest()
 
@@ -299,7 +301,7 @@
         @return: C{True} if the MAC is valid.
         """
         if not self.inMAC[0]:
-            return mac == ''
+            return mac == b''
         data = struct.pack('>L', seqid) + data
         outer = hmac.HMAC(self.inMAC.key, data, self.inMAC[0]).digest()
         return mac == outer
@@ -314,9 +316,9 @@
     @rtype: L{list} of L{str}
     """
     supportedCiphers = []
-    cs = ['aes256-ctr', 'aes256-cbc', 'aes192-ctr', 'aes192-cbc',
-          'aes128-ctr', 'aes128-cbc', 'cast128-ctr', 'cast128-cbc',
-          'blowfish-ctr', 'blowfish-cbc', '3des-ctr', '3des-cbc']
+    cs = [b'aes256-ctr', b'aes256-cbc', b'aes192-ctr', b'aes192-cbc',
+          b'aes128-ctr', b'aes128-cbc', b'cast128-ctr', b'cast128-cbc',
+          b'blowfish-ctr', b'blowfish-cbc', b'3des-ctr', b'3des-cbc']
     for cipher in cs:
         algorithmClass, keySize, modeClass = SSHCiphers.cipherMap[cipher]
         try:
@@ -447,10 +449,10 @@
         to send them while a key exchange is in progress.  When the key
         exchange completes, another attempt is made to send these messages.
     """
-    protocolVersion = '2.0'
-    version = 'Twisted'
-    comment = ''
-    ourVersionString = ('SSH-' + protocolVersion + '-' + version + ' '
+    protocolVersion = b'2.0'
+    version = b'Twisted'
+    comment = b''
+    ourVersionString = (b'SSH-' + protocolVersion + b'-' + version + b' '
             + comment).strip()
 
     # C{none} is supported as cipher and hmac. For security they are disabled
@@ -459,21 +461,21 @@
     # List ordered by preference.
     supportedCiphers = _getSupportedCiphers()
     supportedMACs = [
-        'hmac-sha2-512',
-        'hmac-sha2-256',
-        'hmac-sha1',
-        'hmac-md5',
+        b'hmac-sha2-512',
+        b'hmac-sha2-256',
+        b'hmac-sha1',
+        b'hmac-md5',
         # `none`,
-        ]
+    ]
 
     supportedKeyExchanges = _kex.getSupportedKeyExchanges()
-    supportedPublicKeys = ['ssh-rsa', 'ssh-dss']
-    supportedCompressions = ['none', 'zlib']
+    supportedPublicKeys = [b'ssh-rsa', b'ssh-dss']
+    supportedCompressions = [b'none', b'zlib']
     supportedLanguages = ()
-    supportedVersions = ('1.99', '2.0')
+    supportedVersions = (b'1.99', b'2.0')
     isClient = False
     gotVersion = False
-    buf = ''
+    buf = b''
     outgoingPacketSequence = 0
     incomingPacketSequence = 0
     outgoingCompression = None
@@ -518,9 +520,10 @@
         Called when the connection is made to the other side.  We sent our
         version and the MSG_KEXINIT packet.
         """
-        self.transport.write('%s\r\n' % (self.ourVersionString,))
-        self.currentEncryptions = SSHCiphers('none', 'none', 'none', 'none')
-        self.currentEncryptions.setKeys('', '', '', '', '', '')
+        self.transport.write(self.ourVersionString + b'\r\n')
+        self.currentEncryptions = SSHCiphers(b'none', b'none', b'none',
+                                             b'none')
+        self.currentEncryptions.setKeys(b'', b'', b'', b'', b'', b'')
         self.sendKexInit()
 
 
@@ -539,19 +542,20 @@
                 "Cannot send KEXINIT while key exchange state is %r" % (
                     self._keyExchangeState,))
 
-        self.ourKexInitPayload = (chr(MSG_KEXINIT) +
-               randbytes.secureRandom(16) +
-               NS(','.join(self.supportedKeyExchanges)) +
-               NS(','.join(self.supportedPublicKeys)) +
-               NS(','.join(self.supportedCiphers)) +
-               NS(','.join(self.supportedCiphers)) +
-               NS(','.join(self.supportedMACs)) +
-               NS(','.join(self.supportedMACs)) +
-               NS(','.join(self.supportedCompressions)) +
-               NS(','.join(self.supportedCompressions)) +
-               NS(','.join(self.supportedLanguages)) +
-               NS(','.join(self.supportedLanguages)) +
-               '\000' + '\000\000\000\000')
+        self.ourKexInitPayload = b''.join([
+            chr(MSG_KEXINIT),
+            randbytes.secureRandom(16),
+            NS(b','.join(self.supportedKeyExchanges)),
+            NS(b','.join(self.supportedPublicKeys)),
+            NS(b','.join(self.supportedCiphers)),
+            NS(b','.join(self.supportedCiphers)),
+            NS(b','.join(self.supportedMACs)),
+            NS(b','.join(self.supportedMACs)),
+            NS(b','.join(self.supportedCompressions)),
+            NS(b','.join(self.supportedCompressions)),
+            NS(b','.join(self.supportedLanguages)),
+            NS(b','.join(self.supportedLanguages)),
+            b'\000\000\000\000\000'])
         self.sendPacket(MSG_KEXINIT, self.ourKexInitPayload[1:])
         self._keyExchangeState = self._KEY_EXCHANGE_REQUESTED
         self._blockedByKeyExchange = []
@@ -639,7 +643,7 @@
         packetLen, paddingLen = struct.unpack('!LB', first[:5])
         if packetLen > 1048576: # 1024 ** 2
             self.sendDisconnect(DISCONNECT_PROTOCOL_ERROR,
-                                'bad packet length %s' % (packetLen,))
+                                b'bad packet length %s' % (packetLen,))
             return
         if len(self.buf) < packetLen + 4 + ms:
             # Not enough data for a packet
@@ -648,20 +652,20 @@
         if (packetLen + 4) % bs != 0:
             self.sendDisconnect(
                 DISCONNECT_PROTOCOL_ERROR,
-                'bad packet mod (%i%%%i == %i)' % (packetLen + 4, bs,
+                b'bad packet mod (%i%%%i == %i)' % (packetLen + 4, bs,
                                                    (packetLen + 4) % bs))
             return
         encData, self.buf = self.buf[:4 + packetLen], self.buf[4 + packetLen:]
         packet = first + self.currentEncryptions.decrypt(encData[bs:])
         if len(packet) != 4 + packetLen:
             self.sendDisconnect(DISCONNECT_PROTOCOL_ERROR,
-                                'bad decryption')
+                                b'bad decryption')
             return
         if ms:
             macData, self.buf = self.buf[:ms], self.buf[ms:]
             if not self.currentEncryptions.verify(self.incomingPacketSequence,
                                                   packet, macData):
-                self.sendDisconnect(DISCONNECT_MAC_ERROR, 'bad MAC')
+                self.sendDisconnect(DISCONNECT_MAC_ERROR, b'bad MAC')
                 return
         payload = packet[5:-paddingLen]
         if self.incomingCompression:
@@ -671,7 +675,7 @@
                 # Tolerate any errors in decompression
                 log.err()
                 self.sendDisconnect(DISCONNECT_COMPRESSION_ERROR,
-                                    'compression error')
+                                    b'compression error')
                 return
         self.incomingPacketSequence += 1
         return payload
@@ -687,7 +691,7 @@
         @type remoteVersion: C{str}
         """
         self.sendDisconnect(DISCONNECT_PROTOCOL_VERSION_NOT_SUPPORTED,
-            'bad version ' + remoteVersion)
+            b'bad version ' + remoteVersion)
 
 
     def dataReceived(self, data):
@@ -701,19 +705,19 @@
         """
         self.buf = self.buf + data
         if not self.gotVersion:
-            if self.buf.find('\n', self.buf.find('SSH-')) == -1:
+            if self.buf.find(b'\n', self.buf.find(b'SSH-')) == -1:
                 return
-            lines = self.buf.split('\n')
+            lines = self.buf.split(b'\n')
             for p in lines:
-                if p.startswith('SSH-'):
+                if p.startswith(b'SSH-'):
                     self.gotVersion = True
                     self.otherVersionString = p.strip()
-                    remoteVersion = p.split('-')[1]
+                    remoteVersion = p.split(b'-')[1]
                     if remoteVersion not in self.supportedVersions:
                         self._unsupportedVersionReceived(remoteVersion)
                         return
                     i = lines.index(p)
-                    self.buf = '\n'.join(lines[i + 1:])
+                    self.buf = b'\n'.join(lines[i + 1:])
         packet = self.getPacket()
         while packet:
             messageNum = ord(packet[0])
@@ -840,7 +844,7 @@
         k = getNS(packet[16:], 10)
         strings, rest = k[:-1], k[-1]
         (kexAlgs, keyAlgs, encCS, encSC, macCS, macSC, compCS, compSC, langCS,
-         langSC) = [s.split(',') for s in strings]
+         langSC) = [s.split(b',') for s in strings]
         # These are the server directions
         outs = [encSC, macSC, compSC]
         ins = [encCS, macSC, compCS]
@@ -866,11 +870,11 @@
         if None in (self.kexAlg, self.keyAlg, self.outgoingCompressionType,
                     self.incomingCompressionType):
             self.sendDisconnect(DISCONNECT_KEY_EXCHANGE_FAILED,
-                                "couldn't match all kex parts")
+                                b"couldn't match all kex parts")
             return
         if None in self.nextEncryptions.__dict__.values():
             self.sendDisconnect(DISCONNECT_KEY_EXCHANGE_FAILED,
-                                "couldn't match all kex parts")
+                                b"couldn't match all kex parts")
             return
         log.msg('kex alg, key alg: %s %s' % (self.kexAlg, self.keyAlg))
         log.msg('outgoing: %s %s %s' % (self.nextEncryptions.outCipType,
@@ -963,7 +967,7 @@
         self.service.serviceStarted()
 
 
-    def sendDebug(self, message, alwaysDisplay=False, language=''):
+    def sendDebug(self, message, alwaysDisplay=False, language=b''):
         """
         Send a debug message to the other side.
 
@@ -1011,7 +1015,7 @@
         @type desc: C{str}
         """
         self.sendPacket(
-            MSG_DISCONNECT, struct.pack('>L', reason) + NS(desc) + NS(''))
+            MSG_DISCONNECT, struct.pack('>L', reason) + NS(desc) + NS(b''))
         log.msg('Disconnecting with error, code %s\nreason: %s' % (reason,
                                                                    desc))
         self.transport.loseConnection()
@@ -1054,12 +1058,12 @@
         """
         if not self.sessionID:
             self.sessionID = exchangeHash
-        initIVCS = self._getKey('A', sharedSecret, exchangeHash)
-        initIVSC = self._getKey('B', sharedSecret, exchangeHash)
-        encKeyCS = self._getKey('C', sharedSecret, exchangeHash)
-        encKeySC = self._getKey('D', sharedSecret, exchangeHash)
-        integKeyCS = self._getKey('E', sharedSecret, exchangeHash)
-        integKeySC = self._getKey('F', sharedSecret, exchangeHash)
+        initIVCS = self._getKey(b'A', sharedSecret, exchangeHash)
+        initIVSC = self._getKey(b'B', sharedSecret, exchangeHash)
+        encKeyCS = self._getKey(b'C', sharedSecret, exchangeHash)
+        encKeySC = self._getKey(b'D', sharedSecret, exchangeHash)
+        integKeyCS = self._getKey(b'E', sharedSecret, exchangeHash)
+        integKeySC = self._getKey(b'F', sharedSecret, exchangeHash)
         outs = [initIVSC, encKeySC, integKeySC]
         ins = [initIVCS, encKeyCS, integKeyCS]
         if self.isClient: # Reverse for the client
@@ -1067,7 +1071,7 @@
             outs, ins = ins, outs
         self.nextEncryptions.setKeys(outs[0], outs[1], ins[0], ins[1],
                                      outs[2], ins[2])
-        self.sendPacket(MSG_NEWKEYS, '')
+        self.sendPacket(MSG_NEWKEYS, b'')
 
 
     def _newKeys(self):
@@ -1079,9 +1083,9 @@
         """
         log.msg('NEW KEYS')
         self.currentEncryptions = self.nextEncryptions
-        if self.outgoingCompressionType == 'zlib':
+        if self.outgoingCompressionType == b'zlib':
             self.outgoingCompression = zlib.compressobj(6)
-        if self.incomingCompressionType == 'zlib':
+        if self.incomingCompressionType == b'zlib':
             self.incomingCompression = zlib.decompressobj()
 
         self._keyExchangeState = self._KEY_EXCHANGE_NONE
@@ -1102,9 +1106,9 @@
         @return: C{True} if it is encrypted.
         """
         if direction == "out":
-            return self.currentEncryptions.outCipType != 'none'
+            return self.currentEncryptions.outCipType != b'none'
         elif direction == "in":
-            return self.currentEncryptions.inCipType != 'none'
+            return self.currentEncryptions.inCipType != b'none'
         elif direction == "both":
             return self.isEncrypted("in") and self.isEncrypted("out")
         else:
@@ -1122,9 +1126,9 @@
         @return: C{True} if it is verified.
         """
         if direction == "out":
-            return self.currentEncryptions.outMACType != 'none'
+            return self.currentEncryptions.outMACType != b'none'
         elif direction == "in":
-            return self.currentEncryptions.inMACType != 'none'
+            return self.currentEncryptions.inMACType != b'none'
         elif direction == "both":
             return self.isVerified("in") and self.isVerified("out")
         else:
@@ -1137,7 +1141,7 @@
         DISCONNECT_CONNECTION_LOST message.
         """
         self.sendDisconnect(DISCONNECT_CONNECTION_LOST,
-                            "user closed connection")
+                            b"user closed connection")
 
     # Client methods
 
@@ -1380,9 +1384,9 @@
         @type packet: L{bytes}
         @param packet: The message data.
         """
-        if packet != '':
+        if packet != b'':
             self.sendDisconnect(DISCONNECT_PROTOCOL_ERROR,
-                                "NEWKEYS takes no data")
+                                b"NEWKEYS takes no data")
             return
         self._newKeys()
 
@@ -1403,7 +1407,7 @@
         cls = self.factory.getService(self, service)
         if not cls:
             self.sendDisconnect(DISCONNECT_SERVICE_NOT_AVAILABLE,
-                                "don't have service %s" % service)
+                                b"don't have service " + service)
             return
         else:
             self.sendPacket(MSG_SERVICE_ACCEPT, NS(service))
@@ -1522,13 +1526,13 @@
         pubKey, packet = getNS(packet)
         f, packet = getMP(packet)
         signature, packet = getNS(packet)
-        fingerprint = ':'.join([ch.encode('hex') for ch in
-                                md5(pubKey).digest()])
+        fingerprint = b':'.join([binascii.hexlify(ch) for ch in
+                                 md5(pubKey).digest()])
         d = self.verifyHostKey(pubKey, fingerprint)
         d.addCallback(self._continueKEXDH_REPLY, pubKey, f, signature)
         d.addErrback(
             lambda unused: self.sendDisconnect(
-                DISCONNECT_HOST_KEY_NOT_VERIFIABLE, 'bad host key'))
+                DISCONNECT_HOST_KEY_NOT_VERIFIABLE, b'bad host key'))
         return d
 
 
@@ -1585,7 +1589,7 @@
         exchangeHash = h.digest()
         if not serverKey.verify(signature, exchangeHash):
             self.sendDisconnect(DISCONNECT_KEY_EXCHANGE_FAILED,
-                                'bad signature')
+                                b'bad signature')
             return
         self._keySetup(sharedSecret, exchangeHash)
 
@@ -1613,7 +1617,7 @@
         d.addCallback(self._continueGEX_REPLY, pubKey, f, signature)
         d.addErrback(
             lambda unused: self.sendDisconnect(
-                DISCONNECT_HOST_KEY_NOT_VERIFIABLE, 'bad host key'))
+                DISCONNECT_HOST_KEY_NOT_VERIFIABLE, b'bad host key'))
         return d
 
 
@@ -1653,7 +1657,7 @@
         exchangeHash = h.digest()
         if not serverKey.verify(signature, exchangeHash):
             self.sendDisconnect(DISCONNECT_KEY_EXCHANGE_FAILED,
-                                'bad signature')
+                                b'bad signature')
             return
         self._keySetup(sharedSecret, exchangeHash)
 
@@ -1664,7 +1668,7 @@
         """
         SSHTransportBase._keySetup(self, sharedSecret, exchangeHash)
         if self._gotNewKeys:
-            self.ssh_NEWKEYS('')
+            self.ssh_NEWKEYS(b'')
 
 
     def ssh_NEWKEYS(self, packet):
@@ -1676,9 +1680,9 @@
         @type packet: L{bytes}
         @param packet: The message data.
         """
-        if packet != '':
+        if packet != b'':
             self.sendDisconnect(DISCONNECT_PROTOCOL_ERROR,
-                                "NEWKEYS takes no data")
+                                b"NEWKEYS takes no data")
             return
         if not self.nextEncryptions.encBlockSize:
             self._gotNewKeys = 1
@@ -1697,14 +1701,14 @@
         @type packet: L{bytes}
         @param packet: The message data.
         """
-        if packet == '':
+        if packet == b'':
             log.msg('got SERVICE_ACCEPT without payload')
         else:
             name = getNS(packet)[0]
             if name != self.instance.name:
                 self.sendDisconnect(
                     DISCONNECT_PROTOCOL_ERROR,
-                    "received accept for service we did not request")
+                    b"received accept for service we did not request")
         self.setService(self.instance)
 
 
@@ -1802,7 +1806,7 @@
 
 
 DH_GENERATOR, DH_PRIME = _kex.getDHGeneratorAndPrime(
-    'diffie-hellman-group1-sha1')
+    b'diffie-hellman-group1-sha1')
 
 
 MSG_DISCONNECT = 1

Modified: trunk/twisted/conch/test/test_transport.py
==============================================================================
--- trunk/twisted/conch/test/test_transport.py	(original)
+++ trunk/twisted/conch/test/test_transport.py	Sun Mar 20 19:04:25 2016
@@ -5,7 +5,10 @@
 Tests for ssh/transport.py and the classes therein.
 """
 
+from __future__ import absolute_import, division
+
 import struct
+import binascii
 
 try:
     import pyasn1
@@ -121,21 +124,22 @@
         self.ignoreds.append(packet)
 
 
+
 class MockCipher(object):
     """
     A mocked-up version of twisted.conch.ssh.transport.SSHCiphers.
     """
-    outCipType = 'test'
+    outCipType = b'test'
     encBlockSize = 6
-    inCipType = 'test'
+    inCipType = b'test'
     decBlockSize = 6
-    inMACType = 'test'
-    outMACType = 'test'
+    inMACType = b'test'
+    outMACType = b'test'
     verifyDigestSize = 1
     usedEncrypt = False
     usedDecrypt = False
-    outMAC = (None, '', '', 1)
-    inMAC = (None, '', '', 1)
+    outMAC = (None, b'', b'', 1)
+    inMAC = (None, b'', b'', 1)
     keys = ()
 
 
@@ -193,7 +197,6 @@
     compressing, it reverses the data and adds a 0x66 byte to the end.
     """
 
-
     def compress(self, payload):
         return payload[::-1] # reversed
 
@@ -203,7 +206,7 @@
 
 
     def flush(self, kind):
-        return '\x66'
+        return b'\x66'
 
 
 
@@ -245,6 +248,7 @@
         self.transport.sendPacket(0xff, packet)
 
 
+
 class MockFactory(factory.SSHFactory):
     """
     A mocked-up factory based on twisted.conch.ssh.factory.SSHFactory.
@@ -258,8 +262,8 @@
         Return the public keys that authenticate this server.
         """
         return {
-            'ssh-rsa': keys.Key.fromString(keydata.publicRSA_openssh),
-            'ssh-dsa': keys.Key.fromString(keydata.publicDSA_openssh)}
+            b'ssh-rsa': keys.Key.fromString(keydata.publicRSA_openssh),
+            b'ssh-dsa': keys.Key.fromString(keydata.publicDSA_openssh)}
 
 
     def getPrivateKeys(self):
@@ -267,8 +271,8 @@
         Return the private keys that authenticate this server.
         """
         return {
-            'ssh-rsa': keys.Key.fromString(keydata.privateRSA_openssh),
-            'ssh-dsa': keys.Key.fromString(keydata.privateDSA_openssh)}
+            b'ssh-rsa': keys.Key.fromString(keydata.privateRSA_openssh),
+            b'ssh-dsa': keys.Key.fromString(keydata.privateDSA_openssh)}
 
 
     def getPrimes(self):
@@ -286,9 +290,9 @@
         # See OpenSSHFactory.getPrimes.
         return {
             1024: ((2, _kex.getDHGeneratorAndPrime(
-                'diffie-hellman-group1-sha1')[1]),),
+                b'diffie-hellman-group1-sha1')[1]),),
             2048: ((3, _kex.getDHGeneratorAndPrime(
-                'diffie-hellman-group1-sha1')[1]),),
+                b'diffie-hellman-group1-sha1')[1]),),
             4096: ((5, 7),)}
 
 
@@ -299,7 +303,6 @@
     getPublicKeys().  We return those here for testing.
     """
 
-
     def getPublicKeys(self):
         """
         We used to map key types to public key blobs as strings.
@@ -317,7 +320,6 @@
     objects from getPrivateKeys().  We return those here for testing.
     """
 
-
     def getPrivateKeys(self):
         """
         We used to map key types to cryptography key objects.
@@ -328,6 +330,7 @@
         return keys
 
 
+
 class TransportTestCase(unittest.TestCase):
     """
     Base class for transport test cases.
@@ -337,6 +340,7 @@
     if dependencySkip:
         skip = dependencySkip
 
+
     def setUp(self):
         self.transport = proto_helpers.StringTransport()
         self.proto = self.klass()
@@ -345,7 +349,7 @@
             """
             Return a consistent entropy value
             """
-            return '\x99' * len
+            return b'\x99' * len
         self.patch(randbytes, 'secureRandom', secureRandom)
         def stubSendPacket(messageType, payload):
             self.packets.append((messageType, payload))
@@ -360,10 +364,10 @@
         which is started in L{SSHTransportBase.connectionMade} completes and
         non-key exchange messages can be sent and received.
         """
-        proto.dataReceived("SSH-2.0-BogoClient-1.2i\r\n")
+        proto.dataReceived(b"SSH-2.0-BogoClient-1.2i\r\n")
         proto.dispatchMessage(
             transport.MSG_KEXINIT, self._A_KEXINIT_MESSAGE)
-        proto._keySetup("foo", "bar")
+        proto._keySetup(b"foo", b"bar")
         # SSHTransportBase can't handle MSG_NEWKEYS, or it would be the right
         # thing to deliver next.  _newKeys won't work either, because
         # sendKexInit (probably) hasn't been called.  sendKexInit is
@@ -390,7 +394,7 @@
     Mixin for diffie-hellman-group-exchange-sha1 tests.
     """
 
-    kexAlgorithm = 'diffie-hellman-group-exchange-sha1'
+    kexAlgorithm = b'diffie-hellman-group-exchange-sha1'
     hashProcessor = sha1
 
 
@@ -400,7 +404,7 @@
     Mixin for diffie-hellman-group-exchange-sha256 tests.
     """
 
-    kexAlgorithm = 'diffie-hellman-group-exchange-sha256'
+    kexAlgorithm = b'diffie-hellman-group-exchange-sha256'
     hashProcessor = sha256
 
 
@@ -421,18 +425,18 @@
     """
 
     _A_KEXINIT_MESSAGE = (
-        "\xAA" * 16 +
-        common.NS('diffie-hellman-group1-sha1') +
-        common.NS('ssh-rsa') +
-        common.NS('aes256-ctr') +
-        common.NS('aes256-ctr') +
-        common.NS('hmac-sha1') +
-        common.NS('hmac-sha1') +
-        common.NS('none') +
-        common.NS('none') +
-        common.NS('') +
-        common.NS('') +
-        '\x00' + '\x00\x00\x00\x00')
+        b"\xAA" * 16 +
+        common.NS(b'diffie-hellman-group1-sha1') +
+        common.NS(b'ssh-rsa') +
+        common.NS(b'aes256-ctr') +
+        common.NS(b'aes256-ctr') +
+        common.NS(b'hmac-sha1') +
+        common.NS(b'hmac-sha1') +
+        common.NS(b'none') +
+        common.NS(b'none') +
+        common.NS(b'') +
+        common.NS(b'') +
+        b'\x00' + b'\x00\x00\x00\x00')
 
     def test_sendVersion(self):
         """
@@ -440,8 +444,8 @@
         string.
         """
         # the other setup was done in the setup method
-        self.assertEqual(self.transport.value().split('\r\n', 1)[0],
-                         "SSH-2.0-Twisted")
+        self.assertEqual(self.transport.value().split(b'\r\n', 1)[0],
+                         b"SSH-2.0-Twisted")
 
 
     def test_sendPacketPlain(self):
@@ -458,11 +462,11 @@
         proto.makeConnection(self.transport)
         self.finishKeyExchange(proto)
         self.transport.clear()
-        message = ord('A')
-        payload = 'BCDEFG'
+        message = ord(b'A')
+        payload = b'BCDEFG'
         proto.sendPacket(message, payload)
         value = self.transport.value()
-        self.assertEqual(value, '\x00\x00\x00\x0c\x04ABCDEFG\x99\x99\x99\x99')
+        self.assertEqual(value, b'\x00\x00\x00\x0c\x04ABCDEFG\x99\x99\x99\x99')
 
 
     def test_sendPacketEncrypted(self):
@@ -475,7 +479,7 @@
         self.finishKeyExchange(proto)
         proto.currentEncryptions = testCipher = MockCipher()
         message = ord('A')
-        payload = 'BC'
+        payload = b'BC'
         self.transport.clear()
         proto.sendPacket(message, payload)
         self.assertTrue(testCipher.usedEncrypt)
@@ -483,15 +487,15 @@
         self.assertEqual(
             value,
             # Four byte length prefix
-            '\x00\x00\x00\x08'
+            b'\x00\x00\x00\x08'
             # One byte padding length
-            '\x04'
+            b'\x04'
             # The actual application data
-            'ABC'
+            b'ABC'
             # "Random" padding - see the secureRandom monkeypatch in setUp
-            '\x99\x99\x99\x99'
+            b'\x99\x99\x99\x99'
             # The MAC
-            '\x02')
+            b'\x02')
 
 
     def test_sendPacketCompressed(self):
@@ -504,11 +508,11 @@
         self.finishKeyExchange(proto)
         proto.outgoingCompression = MockCompression()
         self.transport.clear()
-        proto.sendPacket(ord('A'), 'B')
+        proto.sendPacket(ord('A'), b'B')
         value = self.transport.value()
         self.assertEqual(
             value,
-            '\x00\x00\x00\x0c\x08BA\x66\x99\x99\x99\x99\x99\x99\x99\x99')
+            b'\x00\x00\x00\x0c\x08BA\x66\x99\x99\x99\x99\x99\x99\x99\x99')
 
 
     def test_sendPacketBoth(self):
@@ -523,7 +527,7 @@
         proto.currentEncryptions = testCipher = MockCipher()
         proto.outgoingCompression = MockCompression()
         message = ord('A')
-        payload = 'BC'
+        payload = b'BC'
         self.transport.clear()
         proto.sendPacket(message, payload)
         self.assertTrue(testCipher.usedEncrypt)
@@ -531,15 +535,15 @@
         self.assertEqual(
             value,
             # Four byte length prefix
-            '\x00\x00\x00\x0e'
+            b'\x00\x00\x00\x0e'
             # One byte padding length
-            '\x09'
+            b'\x09'
             # Compressed application data
-            'CBA\x66'
+            b'CBA\x66'
             # "Random" padding - see the secureRandom monkeypatch in setUp
-            '\x99\x99\x99\x99\x99\x99\x99\x99\x99'
+            b'\x99\x99\x99\x99\x99\x99\x99\x99\x99'
             # The MAC
-            '\x02')
+            b'\x02')
 
 
     def test_getPacketPlain(self):
@@ -551,10 +555,10 @@
         proto.makeConnection(self.transport)
         self.finishKeyExchange(proto)
         self.transport.clear()
-        proto.sendPacket(ord('A'), 'BC')
-        proto.buf = self.transport.value() + 'extra'
-        self.assertEqual(proto.getPacket(), 'ABC')
-        self.assertEqual(proto.buf, 'extra')
+        proto.sendPacket(ord('A'), b'BC')
+        proto.buf = self.transport.value() + b'extra'
+        self.assertEqual(proto.getPacket(), b'ABC')
+        self.assertEqual(proto.buf, b'extra')
 
 
     def test_getPacketEncrypted(self):
@@ -567,15 +571,15 @@
         proto.makeConnection(self.transport)
         self.transport.clear()
         proto.currentEncryptions = testCipher = MockCipher()
-        proto.sendPacket(ord('A'), 'BCD')
+        proto.sendPacket(ord('A'), b'BCD')
         value = self.transport.value()
         proto.buf = value[:MockCipher.decBlockSize]
         self.assertEqual(proto.getPacket(), None)
         self.assertTrue(testCipher.usedDecrypt)
-        self.assertEqual(proto.first, '\x00\x00\x00\x0e\x09A')
+        self.assertEqual(proto.first, b'\x00\x00\x00\x0e\x09A')
         proto.buf += value[MockCipher.decBlockSize:]
-        self.assertEqual(proto.getPacket(), 'ABCD')
-        self.assertEqual(proto.buf, '')
+        self.assertEqual(proto.getPacket(), b'ABCD')
+        self.assertEqual(proto.buf, b'')
 
 
     def test_getPacketCompressed(self):
@@ -589,9 +593,9 @@
         self.transport.clear()
         proto.outgoingCompression = MockCompression()
         proto.incomingCompression = proto.outgoingCompression
-        proto.sendPacket(ord('A'), 'BCD')
+        proto.sendPacket(ord('A'), b'BCD')
         proto.buf = self.transport.value()
-        self.assertEqual(proto.getPacket(), 'ABCD')
+        self.assertEqual(proto.getPacket(), b'ABCD')
 
 
     def test_getPacketBoth(self):
@@ -606,17 +610,17 @@
         proto.currentEncryptions = MockCipher()
         proto.outgoingCompression = MockCompression()
         proto.incomingCompression = proto.outgoingCompression
-        proto.sendPacket(ord('A'), 'BCDEFG')
+        proto.sendPacket(ord('A'), b'BCDEFG')
         proto.buf = self.transport.value()
-        self.assertEqual(proto.getPacket(), 'ABCDEFG')
+        self.assertEqual(proto.getPacket(), b'ABCDEFG')
 
 
     def test_ciphersAreValid(self):
         """
         Test that all the supportedCiphers are valid.
         """
-        ciphers = transport.SSHCiphers('A', 'B', 'C', 'D')
-        iv = key = '\x00' * 16
+        ciphers = transport.SSHCiphers(b'A', b'B', b'C', b'D')
+        iv = key = b'\x00' * 16
         for cipName in self.proto.supportedCiphers:
             self.assertTrue(ciphers._getCipher(cipName, iv, key))
 
@@ -637,29 +641,29 @@
             bool first packet follows
             uint32 0
         """
-        value = self.transport.value().split('\r\n', 1)[1]
+        value = self.transport.value().split(b'\r\n', 1)[1]
         self.proto.buf = value
         packet = self.proto.getPacket()
-        self.assertEqual(packet[0], chr(transport.MSG_KEXINIT))
-        self.assertEqual(packet[1:17], '\x99' * 16)
+        self.assertEqual(packet[0:1], chr(transport.MSG_KEXINIT))
+        self.assertEqual(packet[1:17], b'\x99' * 16)
         (keyExchanges, pubkeys, ciphers1, ciphers2, macs1, macs2,
          compressions1, compressions2, languages1, languages2,
          buf) = common.getNS(packet[17:], 10)
 
         self.assertEqual(
-            keyExchanges, ','.join(self.proto.supportedKeyExchanges))
-        self.assertEqual(pubkeys, ','.join(self.proto.supportedPublicKeys))
-        self.assertEqual(ciphers1, ','.join(self.proto.supportedCiphers))
-        self.assertEqual(ciphers2, ','.join(self.proto.supportedCiphers))
-        self.assertEqual(macs1, ','.join(self.proto.supportedMACs))
-        self.assertEqual(macs2, ','.join(self.proto.supportedMACs))
+            keyExchanges, b','.join(self.proto.supportedKeyExchanges))
+        self.assertEqual(pubkeys, b','.join(self.proto.supportedPublicKeys))
+        self.assertEqual(ciphers1, b','.join(self.proto.supportedCiphers))
+        self.assertEqual(ciphers2, b','.join(self.proto.supportedCiphers))
+        self.assertEqual(macs1, b','.join(self.proto.supportedMACs))
+        self.assertEqual(macs2, b','.join(self.proto.supportedMACs))
         self.assertEqual(compressions1,
-                         ','.join(self.proto.supportedCompressions))
+                         b','.join(self.proto.supportedCompressions))
         self.assertEqual(compressions2,
-                         ','.join(self.proto.supportedCompressions))
-        self.assertEqual(languages1, ','.join(self.proto.supportedLanguages))
-        self.assertEqual(languages2, ','.join(self.proto.supportedLanguages))
-        self.assertEqual(buf, '\x00' * 5)
+                         b','.join(self.proto.supportedCompressions))
+        self.assertEqual(languages1, b','.join(self.proto.supportedLanguages))
+        self.assertEqual(languages2, b','.join(self.proto.supportedLanguages))
+        self.assertEqual(buf, b'\x00' * 5)
 
 
     def test_receiveKEXINITReply(self):
@@ -720,8 +724,8 @@
         del self.proto.sendPacket
 
         for messageType in disallowedMessageTypes:
-            self.proto.sendPacket(messageType, 'foo')
-            self.assertEqual(self.transport.value(), "")
+            self.proto.sendPacket(messageType, b'foo')
+            self.assertEqual(self.transport.value(), b"")
 
         self.finishKeyExchange(self.proto)
         # Make the bytes written to the transport cleartext so it's easier to
@@ -731,7 +735,7 @@
         # Pseudo-deliver the peer's NEWKEYS message, which should flush the
         # messages which were queued above.
         self.proto._newKeys()
-        self.assertEqual(self.transport.value().count("foo"), 2)
+        self.assertEqual(self.transport.value().count(b"foo"), 2)
 
 
     def test_sendDebug(self):
@@ -741,11 +745,11 @@
             string debug message
             string language
         """
-        self.proto.sendDebug("test", True, 'en')
+        self.proto.sendDebug(b"test", True, b'en')
         self.assertEqual(
             self.packets,
             [(transport.MSG_DEBUG,
-              "\x01\x00\x00\x00\x04test\x00\x00\x00\x02en")])
+              b"\x01\x00\x00\x00\x04test\x00\x00\x00\x02en")])
 
 
     def test_receiveDebug(self):
@@ -754,8 +758,8 @@
         """
         self.proto.dispatchMessage(
             transport.MSG_DEBUG,
-            '\x01\x00\x00\x00\x04test\x00\x00\x00\x02en')
-        self.assertEqual(self.proto.debugs, [(True, 'test', 'en')])
+            b'\x01\x00\x00\x00\x04test\x00\x00\x00\x02en')
+        self.assertEqual(self.proto.debugs, [(True, b'test', b'en')])
 
 
     def test_sendIgnore(self):
@@ -763,10 +767,10 @@
         Test that ignored messages are sent correctly.  Payload::
             string ignored data
         """
-        self.proto.sendIgnore("test")
+        self.proto.sendIgnore(b"test")
         self.assertEqual(
             self.packets, [(transport.MSG_IGNORE,
-                            '\x00\x00\x00\x04test')])
+                            b'\x00\x00\x00\x04test')])
 
 
     def test_receiveIgnore(self):
@@ -774,8 +778,8 @@
         Test that ignored messages are received correctly.  See
         test_sendIgnore.
         """
-        self.proto.dispatchMessage(transport.MSG_IGNORE, 'test')
-        self.assertEqual(self.proto.ignoreds, ['test'])
+        self.proto.dispatchMessage(transport.MSG_IGNORE, b'test')
+        self.assertEqual(self.proto.ignoreds, [b'test'])
 
 
     def test_sendUnimplemented(self):
@@ -786,7 +790,7 @@
         self.proto.sendUnimplemented()
         self.assertEqual(
             self.packets, [(transport.MSG_UNIMPLEMENTED,
-                            '\x00\x00\x00\x00')])
+                            b'\x00\x00\x00\x00')])
 
 
     def test_receiveUnimplemented(self):
@@ -795,7 +799,7 @@
         test_sendUnimplemented.
         """
         self.proto.dispatchMessage(transport.MSG_UNIMPLEMENTED,
-                                   '\x00\x00\x00\xff')
+                                   b'\x00\x00\x00\xff')
         self.assertEqual(self.proto.unimplementeds, [255])
 
 
@@ -810,11 +814,11 @@
         def stubLoseConnection():
             disconnected[0] = True
         self.transport.loseConnection = stubLoseConnection
-        self.proto.sendDisconnect(0xff, "test")
+        self.proto.sendDisconnect(0xff, b"test")
         self.assertEqual(
             self.packets,
             [(transport.MSG_DISCONNECT,
-              "\x00\x00\x00\xff\x00\x00\x00\x04test\x00\x00\x00\x00")])
+              b"\x00\x00\x00\xff\x00\x00\x00\x04test\x00\x00\x00\x00")])
         self.assertTrue(disconnected[0])
 
 
@@ -828,8 +832,8 @@
             disconnected[0] = True
         self.transport.loseConnection = stubLoseConnection
         self.proto.dispatchMessage(transport.MSG_DISCONNECT,
-                                   '\x00\x00\x00\xff\x00\x00\x00\x04test')
-        self.assertEqual(self.proto.errors, [(255, 'test')])
+                                   b'\x00\x00\x00\xff\x00\x00\x00\x04test')
+        self.assertEqual(self.proto.errors, [(255, b'test')])
         self.assertTrue(disconnected[0])
 
 
@@ -858,8 +862,8 @@
         self.proto.setService(service)
         self.assertEqual(self.proto.service, service)
         self.assertTrue(service.started)
-        self.proto.dispatchMessage(0xff, "test")
-        self.assertEqual(self.packets, [(0xff, "test")])
+        self.proto.dispatchMessage(0xff, b"test")
+        self.assertEqual(self.packets, [(0xff, b"test")])
 
         service2 = MockService()
         self.proto.setService(service2)
@@ -895,8 +899,8 @@
         self.assertTrue(self.proto.isEncrypted('in'))
         self.assertTrue(self.proto.isEncrypted('out'))
         self.assertTrue(self.proto.isEncrypted('both'))
-        self.proto.currentEncryptions = transport.SSHCiphers('none', 'none',
-                                                             'none', 'none')
+        self.proto.currentEncryptions = transport.SSHCiphers(b'none', b'none',
+                                                             b'none', b'none')
         self.assertFalse(self.proto.isEncrypted('in'))
         self.assertFalse(self.proto.isEncrypted('out'))
         self.assertFalse(self.proto.isEncrypted('both'))
@@ -915,8 +919,8 @@
         self.assertTrue(self.proto.isVerified('in'))
         self.assertTrue(self.proto.isVerified('out'))
         self.assertTrue(self.proto.isVerified('both'))
-        self.proto.currentEncryptions = transport.SSHCiphers('none', 'none',
-                                                             'none', 'none')
+        self.proto.currentEncryptions = transport.SSHCiphers(b'none', b'none',
+                                                             b'none', b'none')
         self.assertFalse(self.proto.isVerified('in'))
         self.assertFalse(self.proto.isVerified('out'))
         self.assertFalse(self.proto.isVerified('both'))
@@ -950,16 +954,16 @@
             def stubLoseConnection():
                 disconnected[0] = True
             self.transport.loseConnection = stubLoseConnection
-            for c in version + '\r\n':
+            for c in version + b'\r\n':
                 self.proto.dataReceived(c)
             self.assertTrue(disconnected[0])
             self.assertEqual(self.packets[0][0], transport.MSG_DISCONNECT)
             self.assertEqual(
                 self.packets[0][1][3],
                 chr(transport.DISCONNECT_PROTOCOL_VERSION_NOT_SUPPORTED))
-        testBad('SSH-1.5-OpenSSH')
-        testBad('SSH-3.0-Twisted')
-        testBad('GET / HTTP/1.1')
+        testBad(b'SSH-1.5-OpenSSH')
+        testBad(b'SSH-3.0-Twisted')
+        testBad(b'GET / HTTP/1.1')
 
 
     def test_dataBeforeVersion(self):
@@ -968,9 +972,9 @@
         """
         proto = MockTransportBase()
         proto.makeConnection(proto_helpers.StringTransport())
-        data = ("""here's some stuff beforehand
+        data = (b"""here's some stuff beforehand
 here's some other stuff
-""" + proto.ourVersionString + "\r\n")
+""" + proto.ourVersionString + b"\r\n")
         [proto.dataReceived(c) for c in data]
         self.assertTrue(proto.gotVersion)
         self.assertEqual(proto.otherVersionString, proto.ourVersionString)
@@ -983,9 +987,9 @@
         """
         proto = MockTransportBase()
         proto.makeConnection(proto_helpers.StringTransport())
-        proto.dataReceived("SSH-1.99-OpenSSH\n")
+        proto.dataReceived(b"SSH-1.99-OpenSSH\n")
         self.assertTrue(proto.gotVersion)
-        self.assertEqual(proto.otherVersionString, "SSH-1.99-OpenSSH")
+        self.assertEqual(proto.otherVersionString, b"SSH-1.99-OpenSSH")
 
 
     def test_supportedVersionsAreAllowed(self):
@@ -994,9 +998,9 @@
         C{supportedVersions}, an unsupported version error is not emitted.
         """
         proto = MockTransportBase()
-        proto.supportedVersions = ("9.99", )
+        proto.supportedVersions = (b"9.99", )
         proto.makeConnection(proto_helpers.StringTransport())
-        proto.dataReceived("SSH-9.99-OpenSSH\n")
+        proto.dataReceived(b"SSH-9.99-OpenSSH\n")
         self.assertFalse(proto.gotUnsupportedVersion)
 
 
@@ -1006,10 +1010,10 @@
         C{supportedVersions}, an unsupported version error is emitted.
         """
         proto = MockTransportBase()
-        proto.supportedVersions = ("2.0", )
+        proto.supportedVersions = (b"2.0", )
         proto.makeConnection(proto_helpers.StringTransport())
-        proto.dataReceived("SSH-9.99-OpenSSH\n")
-        self.assertEqual("9.99", proto.gotUnsupportedVersion)
+        proto.dataReceived(b"SSH-9.99-OpenSSH\n")
+        self.assertEqual(b"9.99", proto.gotUnsupportedVersion)
 
 
     def test_badPackets(self):
@@ -1025,20 +1029,20 @@
             self.assertEqual(self.packets[0][0], transport.MSG_DISCONNECT)
             self.assertEqual(self.packets[0][1][3], chr(error))
 
-        testBad('\xff' * 8) # big packet
-        testBad('\x00\x00\x00\x05\x00BCDE') # length not modulo blocksize
+        testBad(b'\xff' * 8) # big packet
+        testBad(b'\x00\x00\x00\x05\x00BCDE') # length not modulo blocksize
         oldEncryptions = self.proto.currentEncryptions
         self.proto.currentEncryptions = MockCipher()
-        testBad('\x00\x00\x00\x08\x06AB123456', # bad MAC
+        testBad(b'\x00\x00\x00\x08\x06AB123456', # bad MAC
                 transport.DISCONNECT_MAC_ERROR)
         self.proto.currentEncryptions.decrypt = lambda x: x[:-1]
-        testBad('\x00\x00\x00\x08\x06BCDEFGHIJK') # bad decryption
+        testBad(b'\x00\x00\x00\x08\x06BCDEFGHIJK') # bad decryption
         self.proto.currentEncryptions = oldEncryptions
         self.proto.incomingCompression = MockCompression()
         def stubDecompress(payload):
             raise Exception('bad compression')
         self.proto.incomingCompression.decompress = stubDecompress
-        testBad('\x00\x00\x00\x04\x00BCDE', # bad decompression
+        testBad(b'\x00\x00\x00\x04\x00BCDE', # bad decompression
                 transport.DISCONNECT_COMPRESSION_ERROR)
         self.flushLoggedErrors()
 
@@ -1056,17 +1060,17 @@
             self.proto.packets = []
             seqnum += 1
 
-        self.proto.dispatchMessage(40, '')
+        self.proto.dispatchMessage(40, b'')
         checkUnimplemented()
-        transport.messages[41] = 'MSG_fiction'
-        self.proto.dispatchMessage(41, '')
+        transport.messages[41] = b'MSG_fiction'
+        self.proto.dispatchMessage(41, b'')
         checkUnimplemented()
-        self.proto.dispatchMessage(60, '')
+        self.proto.dispatchMessage(60, b'')
         checkUnimplemented()
         self.proto.setService(MockService())
-        self.proto.dispatchMessage(70, '')
+        self.proto.dispatchMessage(70, b'')
         checkUnimplemented()
-        self.proto.dispatchMessage(71, '')
+        self.proto.dispatchMessage(71, b'')
         checkUnimplemented()
 
 
@@ -1082,7 +1086,7 @@
         proto.setService(MockService())
         proto2 = MockTransportBase()
         proto2.makeConnection(proto_helpers.StringTransport())
-        proto2.sendIgnore('')
+        proto2.sendIgnore(b'')
         self.assertNotEqual(proto.gotVersion, proto2.gotVersion)
         self.assertNotEqual(proto.transport, proto2.transport)
         self.assertNotEqual(proto.outgoingPacketSequence,
@@ -1105,12 +1109,12 @@
         Test that _getKey generates the correct keys.
         """
         self.proto.kexAlg = self.kexAlgorithm
-        self.proto.sessionID = 'EF'
+        self.proto.sessionID = b'EF'
 
         k1 = self.hashProcessor(
-            'AB' + 'CD' + 'K' + self.proto.sessionID).digest()
-        k2 = self.hashProcessor('ABCD' + k1).digest()
-        self.assertEqual(self.proto._getKey('K', 'AB', 'CD'), k1 + k2)
+            b'AB' + b'CD' + b'K' + self.proto.sessionID).digest()
+        k2 = self.hashProcessor(b'ABCD' + k1).digest()
+        self.assertEqual(self.proto._getKey(b'K', b'AB', b'CD'), k1 + k2)
 
 
 
@@ -1137,7 +1141,6 @@
     Tests that need to be run on both the server and the client.
     """
 
-
     def checkDisconnected(self, kind=None):
         """
         Helper function to check if the transport disconnected.
@@ -1210,6 +1213,7 @@
             proto2.supportedMACs = []
         self.connectModifiedProtocol(blankMACs)
 
+
     def test_getPeer(self):
         """
         Test that the transport's L{getPeer} method returns an
@@ -1219,6 +1223,7 @@
                          address.SSHTransportAddress(
                              self.proto.transport.getPeer()))
 
+
     def test_getHost(self):
         """
         Test that the transport's L{getHost} method returns an
@@ -1262,35 +1267,36 @@
         set up the first common algorithm found in the client's preference
         list.
         """
-        self.proto.dataReceived( 'SSH-2.0-Twisted\r\n\x00\x00\x01\xf4\x04\x14'
-                '\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99'
-                '\x99\x00\x00\x00bdiffie-hellman-group1-sha1,diffie-hellman-g'
-                'roup-exchange-sha1,diffie-hellman-group-exchange-sha256\x00'
-                '\x00\x00\x0fssh-dss,ssh-rsa\x00\x00\x00\x85aes128-ctr,aes128-'
-                'cbc,aes192-ctr,aes192-cbc,aes256-ctr,aes256-cbc,cast128-ctr,c'
-                'ast128-cbc,blowfish-ctr,blowfish-cbc,3des-ctr,3des-cbc\x00'
-                '\x00\x00\x85aes128-ctr,aes128-cbc,aes192-ctr,aes192-cbc,aes25'
-                '6-ctr,aes256-cbc,cast128-ctr,cast128-cbc,blowfish-ctr,blowfis'
-                'h-cbc,3des-ctr,3des-cbc\x00\x00\x00\x12hmac-md5,hmac-sha1\x00'
-                '\x00\x00\x12hmac-md5,hmac-sha1\x00\x00\x00\tnone,zlib\x00\x00'
-                '\x00\tnone,zlib\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
-                '\x00\x00\x99\x99\x99\x99')
+        self.proto.dataReceived(
+            b'SSH-2.0-Twisted\r\n\x00\x00\x01\xf4\x04\x14'
+            b'\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99'
+            b'\x99\x00\x00\x00bdiffie-hellman-group1-sha1,diffie-hellman-g'
+            b'roup-exchange-sha1,diffie-hellman-group-exchange-sha256\x00'
+            b'\x00\x00\x0fssh-dss,ssh-rsa\x00\x00\x00\x85aes128-ctr,aes128-'
+            b'cbc,aes192-ctr,aes192-cbc,aes256-ctr,aes256-cbc,cast128-ctr,c'
+            b'ast128-cbc,blowfish-ctr,blowfish-cbc,3des-ctr,3des-cbc\x00'
+            b'\x00\x00\x85aes128-ctr,aes128-cbc,aes192-ctr,aes192-cbc,aes25'
+            b'6-ctr,aes256-cbc,cast128-ctr,cast128-cbc,blowfish-ctr,blowfis'
+            b'h-cbc,3des-ctr,3des-cbc\x00\x00\x00\x12hmac-md5,hmac-sha1\x00'
+            b'\x00\x00\x12hmac-md5,hmac-sha1\x00\x00\x00\tnone,zlib\x00\x00'
+            b'\x00\tnone,zlib\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+            b'\x00\x00\x99\x99\x99\x99')
 
         # Even if as server we prefer diffie-hellman-group-exchange-sha256 the
         # client preference is used.
         self.assertEqual(self.proto.kexAlg,
-                         'diffie-hellman-group1-sha1')
+                         b'diffie-hellman-group1-sha1')
         self.assertEqual(self.proto.keyAlg,
-                         'ssh-dss')
+                         b'ssh-dss')
         self.assertEqual(self.proto.outgoingCompressionType,
-                         'none')
+                         b'none')
         self.assertEqual(self.proto.incomingCompressionType,
-                         'none')
+                         b'none')
         ne = self.proto.nextEncryptions
-        self.assertEqual(ne.outCipType, 'aes128-ctr')
-        self.assertEqual(ne.inCipType, 'aes128-ctr')
-        self.assertEqual(ne.outMACType, 'hmac-md5')
-        self.assertEqual(ne.inMACType, 'hmac-md5')
+        self.assertEqual(ne.outCipType, b'aes128-ctr')
+        self.assertEqual(ne.inCipType, b'aes128-ctr')
+        self.assertEqual(ne.outMACType, b'hmac-md5')
+        self.assertEqual(ne.inMACType, b'hmac-md5')
 
 
     def test_ignoreGuessPacketKex(self):
@@ -1301,9 +1307,9 @@
         the packet is ignored in the case of the key exchange method not
         matching.
         """
-        kexInitPacket = '\x00' * 16 + (
-            ''.join([common.NS(x) for x in
-                     [','.join(y) for y in
+        kexInitPacket = b'\x00' * 16 + (
+            b''.join([common.NS(x) for x in
+                     [b','.join(y) for y in
                       [self.proto.supportedKeyExchanges[::-1],
                        self.proto.supportedPublicKeys,
                        self.proto.supportedCiphers,
@@ -1314,19 +1320,18 @@
                        self.proto.supportedCompressions,
                        self.proto.supportedLanguages,
                        self.proto.supportedLanguages]]])) + (
-            '\xff\x00\x00\x00\x00')
+            b'\xff\x00\x00\x00\x00')
         self.proto.ssh_KEXINIT(kexInitPacket)
         self.assertTrue(self.proto.ignoreNextPacket)
-        self.proto.ssh_DEBUG("\x01\x00\x00\x00\x04test\x00\x00\x00\x00")
+        self.proto.ssh_DEBUG(b"\x01\x00\x00\x00\x04test\x00\x00\x00\x00")
         self.assertTrue(self.proto.ignoreNextPacket)
 
-
-        self.proto.ssh_KEX_DH_GEX_REQUEST_OLD('\x00\x00\x08\x00')
+        self.proto.ssh_KEX_DH_GEX_REQUEST_OLD(b'\x00\x00\x08\x00')
         self.assertFalse(self.proto.ignoreNextPacket)
         self.assertEqual(self.packets, [])
         self.proto.ignoreNextPacket = True
 
-        self.proto.ssh_KEX_DH_GEX_REQUEST('\x00\x00\x08\x00' * 3)
+        self.proto.ssh_KEX_DH_GEX_REQUEST(b'\x00\x00\x08\x00' * 3)
         self.assertFalse(self.proto.ignoreNextPacket)
         self.assertEqual(self.packets, [])
 
@@ -1336,9 +1341,9 @@
         Like test_ignoreGuessPacketKex, but for an incorrectly guessed
         public key format.
         """
-        kexInitPacket = '\x00' * 16 + (
-            ''.join([common.NS(x) for x in
-                     [','.join(y) for y in
+        kexInitPacket = b'\x00' * 16 + (
+            b''.join([common.NS(x) for x in
+                     [b','.join(y) for y in
                       [self.proto.supportedKeyExchanges,
                        self.proto.supportedPublicKeys[::-1],
                        self.proto.supportedCiphers,
@@ -1349,18 +1354,18 @@
                        self.proto.supportedCompressions,
                        self.proto.supportedLanguages,
                        self.proto.supportedLanguages]]])) + (
-            '\xff\x00\x00\x00\x00')
+            b'\xff\x00\x00\x00\x00')
         self.proto.ssh_KEXINIT(kexInitPacket)
         self.assertTrue(self.proto.ignoreNextPacket)
-        self.proto.ssh_DEBUG("\x01\x00\x00\x00\x04test\x00\x00\x00\x00")
+        self.proto.ssh_DEBUG(b"\x01\x00\x00\x00\x04test\x00\x00\x00\x00")
         self.assertTrue(self.proto.ignoreNextPacket)
 
-        self.proto.ssh_KEX_DH_GEX_REQUEST_OLD('\x00\x00\x08\x00')
+        self.proto.ssh_KEX_DH_GEX_REQUEST_OLD(b'\x00\x00\x08\x00')
         self.assertFalse(self.proto.ignoreNextPacket)
         self.assertEqual(self.packets, [])
         self.proto.ignoreNextPacket = True
 
-        self.proto.ssh_KEX_DH_GEX_REQUEST('\x00\x00\x08\x00' * 3)
+        self.proto.ssh_KEX_DH_GEX_REQUEST(b'\x00\x00\x08\x00' * 3)
         self.assertFalse(self.proto.ignoreNextPacket)
         self.assertEqual(self.packets, [])
 
@@ -1374,35 +1379,35 @@
         @type kexAlgorithm: C{str}
         """
         self.proto.supportedKeyExchanges = [kexAlgorithm]
-        self.proto.supportedPublicKeys = ['ssh-rsa']
+        self.proto.supportedPublicKeys = [b'ssh-rsa']
         self.proto.dataReceived(self.transport.value())
 
         g, p = _kex.getDHGeneratorAndPrime(kexAlgorithm)
         e = pow(g, 5000, p)
 
         self.proto.ssh_KEX_DH_GEX_REQUEST_OLD(common.MP(e))
-        y = common.getMP('\x00\x00\x00\x40' + '\x99' * 64)[0]
+        y = common.getMP(b'\x00\x00\x00\x40' + b'\x99' * 64)[0]
         f = common._MPpow(self.proto.g, y, self.proto.p)
         sharedSecret = common._MPpow(e, y, self.proto.p)
 
         h = sha1()
         h.update(common.NS(self.proto.ourVersionString) * 2)
         h.update(common.NS(self.proto.ourKexInitPayload) * 2)
-        h.update(common.NS(self.proto.factory.publicKeys['ssh-rsa'].blob()))
+        h.update(common.NS(self.proto.factory.publicKeys[b'ssh-rsa'].blob()))
         h.update(common.MP(e))
         h.update(f)
         h.update(sharedSecret)
         exchangeHash = h.digest()
 
-        signature = self.proto.factory.privateKeys['ssh-rsa'].sign(
+        signature = self.proto.factory.privateKeys[b'ssh-rsa'].sign(
             exchangeHash)
 
         self.assertEqual(
             self.packets,
             [(transport.MSG_KEXDH_REPLY,
-              common.NS(self.proto.factory.publicKeys['ssh-rsa'].blob())
+              common.NS(self.proto.factory.publicKeys[b'ssh-rsa'].blob())
               + f + common.NS(signature)),
-             (transport.MSG_NEWKEYS, '')])
+             (transport.MSG_NEWKEYS, b'')])
 
 
     def test_KEXDH_INIT_GROUP1(self):
@@ -1410,7 +1415,7 @@
         KEXDH_INIT messages are processed when the
         diffie-hellman-group1-sha1 key exchange algorithm is requested.
         """
-        self.assertKexDHInitResponse('diffie-hellman-group1-sha1')
+        self.assertKexDHInitResponse(b'diffie-hellman-group1-sha1')
 
 
     def test_KEXDH_INIT_GROUP14(self):
@@ -1418,21 +1423,22 @@
         KEXDH_INIT messages are processed when the
         diffie-hellman-group14-sha1 key exchange algorithm is requested.
         """
-        self.assertKexDHInitResponse('diffie-hellman-group14-sha1')
+        self.assertKexDHInitResponse(b'diffie-hellman-group14-sha1')
 
 
     def test_keySetup(self):
         """
         Test that _keySetup sets up the next encryption keys.
         """
-        self.proto.kexAlg = 'diffie-hellman-group1-sha1'
+        self.proto.kexAlg = b'diffie-hellman-group1-sha1'
         self.proto.nextEncryptions = MockCipher()
-        self.simulateKeyExchange('AB', 'CD')
-        self.assertEqual(self.proto.sessionID, 'CD')
-        self.simulateKeyExchange('AB', 'EF')
-        self.assertEqual(self.proto.sessionID, 'CD')
-        self.assertEqual(self.packets[-1], (transport.MSG_NEWKEYS, ''))
-        newKeys = [self.proto._getKey(c, 'AB', 'EF') for c in 'ABCDEF']
+        self.simulateKeyExchange(b'AB', b'CD')
+        self.assertEqual(self.proto.sessionID, b'CD')
+        self.simulateKeyExchange(b'AB', b'EF')
+        self.assertEqual(self.proto.sessionID, b'CD')
+        self.assertEqual(self.packets[-1], (transport.MSG_NEWKEYS, b''))
+        newKeys = [self.proto._getKey(c, b'AB', b'EF')
+                   for c in b'ABCDEF']
         self.assertEqual(
             self.proto.nextEncryptions.keys,
             (newKeys[1], newKeys[3], newKeys[0], newKeys[2], newKeys[5],
@@ -1446,20 +1452,20 @@
         """
         self.test_KEXINITMultipleAlgorithms()
 
-        self.proto.nextEncryptions = transport.SSHCiphers('none', 'none',
-                                                          'none', 'none')
-        self.proto.ssh_NEWKEYS('')
+        self.proto.nextEncryptions = transport.SSHCiphers(b'none', b'none',
+                                                          b'none', b'none')
+        self.proto.ssh_NEWKEYS(b'')
         self.assertIs(self.proto.currentEncryptions,
                       self.proto.nextEncryptions)
         self.assertIs(self.proto.outgoingCompression, None)
         self.assertIs(self.proto.incomingCompression, None)
-        self.proto.outgoingCompressionType = 'zlib'
-        self.simulateKeyExchange('AB', 'CD')
-        self.proto.ssh_NEWKEYS('')
+        self.proto.outgoingCompressionType = b'zlib'
+        self.simulateKeyExchange(b'AB', b'CD')
+        self.proto.ssh_NEWKEYS(b'')
         self.assertIsNot(self.proto.outgoingCompression, None)
-        self.proto.incomingCompressionType = 'zlib'
-        self.simulateKeyExchange('AB', 'EF')
-        self.proto.ssh_NEWKEYS('')
+        self.proto.incomingCompressionType = b'zlib'
+        self.simulateKeyExchange(b'AB', b'EF')
+        self.proto.ssh_NEWKEYS(b'')
         self.assertIsNot(self.proto.incomingCompression, None)
 
 
@@ -1468,9 +1474,9 @@
         Test that the SERVICE_REQUEST message requests and starts a
         service.
         """
-        self.proto.ssh_SERVICE_REQUEST(common.NS('ssh-userauth'))
+        self.proto.ssh_SERVICE_REQUEST(common.NS(b'ssh-userauth'))
         self.assertEqual(self.packets, [(transport.MSG_SERVICE_ACCEPT,
-                                         common.NS('ssh-userauth'))])
+                                         common.NS(b'ssh-userauth'))])
         self.assertEqual(self.proto.service.name, 'MockService')
 
 
@@ -1478,7 +1484,7 @@
         """
         Test that NEWKEYS disconnects if it receives data.
         """
-        self.proto.ssh_NEWKEYS("bad packet")
+        self.proto.ssh_NEWKEYS(b"bad packet")
         self.checkDisconnected()
 
 
@@ -1487,7 +1493,7 @@
         Test that SERVICE_REQUESTS disconnects if an unknown service is
         requested.
         """
-        self.proto.ssh_SERVICE_REQUEST(common.NS('no service'))
+        self.proto.ssh_SERVICE_REQUEST(common.NS(b'no service'))
         self.checkDisconnected(transport.DISCONNECT_SERVICE_NOT_AVAILABLE)
 
 
@@ -1504,14 +1510,14 @@
         Diffie-Hellman group.
         """
         self.proto.supportedKeyExchanges = [self.kexAlgorithm]
-        self.proto.supportedPublicKeys = ['ssh-rsa']
+        self.proto.supportedPublicKeys = [b'ssh-rsa']
         self.proto.dataReceived(self.transport.value())
-        self.proto.ssh_KEX_DH_GEX_REQUEST_OLD('\x00\x00\x04\x00')
+        self.proto.ssh_KEX_DH_GEX_REQUEST_OLD(b'\x00\x00\x04\x00')
         dhGenerator, dhPrime = self.proto.factory.getPrimes().get(1024)[0]
         self.assertEqual(
             self.packets,
             [(transport.MSG_KEX_DH_GEX_GROUP,
-              common.MP(dhPrime) + '\x00\x00\x00\x01\x02')])
+              common.MP(dhPrime) + b'\x00\x00\x00\x01\x02')])
         self.assertEqual(self.proto.g, 2)
         self.assertEqual(self.proto.p, dhPrime)
 
@@ -1533,15 +1539,15 @@
         group.
         """
         self.proto.supportedKeyExchanges = [self.kexAlgorithm]
-        self.proto.supportedPublicKeys = ['ssh-rsa']
+        self.proto.supportedPublicKeys = [b'ssh-rsa']
         self.proto.dataReceived(self.transport.value())
-        self.proto.ssh_KEX_DH_GEX_REQUEST('\x00\x00\x04\x00\x00\x00\x08\x00' +
-                                          '\x00\x00\x0c\x00')
+        self.proto.ssh_KEX_DH_GEX_REQUEST(b'\x00\x00\x04\x00\x00\x00\x08\x00' +
+                                          b'\x00\x00\x0c\x00')
         dhGenerator, dhPrime = self.proto.factory.getPrimes().get(1024)[0]
         self.assertEqual(
             self.packets,
             [(transport.MSG_KEX_DH_GEX_GROUP,
-              common.MP(dhPrime) + '\x00\x00\x00\x01\x03')])
+              common.MP(dhPrime) + b'\x00\x00\x00\x01\x03')])
         self.assertEqual(self.proto.g, 3)
         self.assertEqual(self.proto.p, dhPrime)
 
@@ -1554,14 +1560,14 @@
         """
         self.test_KEX_DH_GEX_REQUEST_OLD()
         e = pow(self.proto.g, 3, self.proto.p)
-        y = common.getMP('\x00\x00\x00\x80' + '\x99' * 128)[0]
+        y = common.getMP(b'\x00\x00\x00\x80' + b'\x99' * 128)[0]
         f = common._MPpow(self.proto.g, y, self.proto.p)
         sharedSecret = common._MPpow(e, y, self.proto.p)
         h = self.hashProcessor()
         h.update(common.NS(self.proto.ourVersionString) * 2)
         h.update(common.NS(self.proto.ourKexInitPayload) * 2)
-        h.update(common.NS(self.proto.factory.publicKeys['ssh-rsa'].blob()))
-        h.update('\x00\x00\x04\x00')
+        h.update(common.NS(self.proto.factory.publicKeys[b'ssh-rsa'].blob()))
+        h.update(b'\x00\x00\x04\x00')
         h.update(common.MP(self.proto.p))
         h.update(common.MP(self.proto.g))
         h.update(common.MP(e))
@@ -1572,10 +1578,10 @@
         self.assertEqual(
             self.packets[1:],
             [(transport.MSG_KEX_DH_GEX_REPLY,
-              common.NS(self.proto.factory.publicKeys['ssh-rsa'].blob()) +
-              f + common.NS(self.proto.factory.privateKeys['ssh-rsa'].sign(
+              common.NS(self.proto.factory.publicKeys[b'ssh-rsa'].blob()) +
+              f + common.NS(self.proto.factory.privateKeys[b'ssh-rsa'].sign(
                             exchangeHash))),
-             (transport.MSG_NEWKEYS, '')])
+             (transport.MSG_NEWKEYS, b'')])
 
 
     def test_KEX_DH_GEX_INIT_after_REQUEST(self):
@@ -1586,14 +1592,14 @@
         """
         self.test_KEX_DH_GEX_REQUEST()
         e = pow(self.proto.g, 3, self.proto.p)
-        y = common.getMP('\x00\x00\x00\x80' + '\x99' * 128)[0]
+        y = common.getMP(b'\x00\x00\x00\x80' + b'\x99' * 128)[0]
         f = common._MPpow(self.proto.g, y, self.proto.p)
         sharedSecret = common._MPpow(e, y, self.proto.p)
         h = self.hashProcessor()
         h.update(common.NS(self.proto.ourVersionString) * 2)
         h.update(common.NS(self.proto.ourKexInitPayload) * 2)
-        h.update(common.NS(self.proto.factory.publicKeys['ssh-rsa'].blob()))
-        h.update('\x00\x00\x04\x00\x00\x00\x08\x00\x00\x00\x0c\x00')
+        h.update(common.NS(self.proto.factory.publicKeys[b'ssh-rsa'].blob()))
+        h.update(b'\x00\x00\x04\x00\x00\x00\x08\x00\x00\x00\x0c\x00')
         h.update(common.MP(self.proto.p))
         h.update(common.MP(self.proto.g))
         h.update(common.MP(e))
@@ -1604,8 +1610,8 @@
         self.assertEqual(
             self.packets[1],
             (transport.MSG_KEX_DH_GEX_REPLY,
-             common.NS(self.proto.factory.publicKeys['ssh-rsa'].blob()) +
-             f + common.NS(self.proto.factory.privateKeys['ssh-rsa'].sign(
+             common.NS(self.proto.factory.publicKeys[b'ssh-rsa'].blob()) +
+             f + common.NS(self.proto.factory.privateKeys[b'ssh-rsa'].sign(
                  exchangeHash))))
 
 
@@ -1642,8 +1648,8 @@
         """
         self.calledVerifyHostKey = True
         self.assertEqual(pubKey, self.blob)
-        self.assertEqual(fingerprint.replace(':', ''),
-                          md5(pubKey).hexdigest())
+        self.assertEqual(fingerprint.replace(b':', b''),
+                         binascii.hexlify(md5(pubKey).digest()))
         return defer.succeed(True)
 
 
@@ -1667,35 +1673,36 @@
         algorithms will set up the first common algorithm, ordered after our
         preference.
         """
-        self.proto.dataReceived( 'SSH-2.0-Twisted\r\n\x00\x00\x01\xf4\x04\x14'
-                '\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99'
-                '\x99\x00\x00\x00bdiffie-hellman-group1-sha1,diffie-hellman-g'
-                'roup-exchange-sha1,diffie-hellman-group-exchange-sha256\x00'
-                '\x00\x00\x0fssh-dss,ssh-rsa\x00\x00\x00\x85aes128-ctr,aes128-'
-                'cbc,aes192-ctr,aes192-cbc,aes256-ctr,aes256-cbc,cast128-ctr,c'
-                'ast128-cbc,blowfish-ctr,blowfish-cbc,3des-ctr,3des-cbc\x00'
-                '\x00\x00\x85aes128-ctr,aes128-cbc,aes192-ctr,aes192-cbc,aes25'
-                '6-ctr,aes256-cbc,cast128-ctr,cast128-cbc,blowfish-ctr,blowfis'
-                'h-cbc,3des-ctr,3des-cbc\x00\x00\x00\x12hmac-md5,hmac-sha1\x00'
-                '\x00\x00\x12hmac-md5,hmac-sha1\x00\x00\x00\tzlib,none\x00\x00'
-                '\x00\tzlib,none\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
-                '\x00\x00\x99\x99\x99\x99')
+        self.proto.dataReceived(
+            b'SSH-2.0-Twisted\r\n\x00\x00\x01\xf4\x04\x14'
+            b'\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99\x99'
+            b'\x99\x00\x00\x00bdiffie-hellman-group1-sha1,diffie-hellman-g'
+            b'roup-exchange-sha1,diffie-hellman-group-exchange-sha256\x00'
+            b'\x00\x00\x0fssh-dss,ssh-rsa\x00\x00\x00\x85aes128-ctr,aes128-'
+            b'cbc,aes192-ctr,aes192-cbc,aes256-ctr,aes256-cbc,cast128-ctr,c'
+            b'ast128-cbc,blowfish-ctr,blowfish-cbc,3des-ctr,3des-cbc\x00'
+            b'\x00\x00\x85aes128-ctr,aes128-cbc,aes192-ctr,aes192-cbc,aes25'
+            b'6-ctr,aes256-cbc,cast128-ctr,cast128-cbc,blowfish-ctr,blowfis'
+            b'h-cbc,3des-ctr,3des-cbc\x00\x00\x00\x12hmac-md5,hmac-sha1\x00'
+            b'\x00\x00\x12hmac-md5,hmac-sha1\x00\x00\x00\tzlib,none\x00\x00'
+            b'\x00\tzlib,none\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+            b'\x00\x00\x99\x99\x99\x99')
         # Even if client prefer diffie-hellman-group1-sha1, we will go for
         # diffie-hellman-group-exchange-sha256 as this what we prefer and is
         # also supported by the server.
         self.assertEqual(self.proto.kexAlg,
-                          'diffie-hellman-group-exchange-sha256')
+                         b'diffie-hellman-group-exchange-sha256')
         self.assertEqual(self.proto.keyAlg,
-                          'ssh-rsa')
+                         b'ssh-rsa')
         self.assertEqual(self.proto.outgoingCompressionType,
-                          'none')
+                         b'none')
         self.assertEqual(self.proto.incomingCompressionType,
-                          'none')
+                         b'none')
         ne = self.proto.nextEncryptions
-        self.assertEqual(ne.outCipType, 'aes256-ctr')
-        self.assertEqual(ne.inCipType, 'aes256-ctr')
-        self.assertEqual(ne.outMACType, 'hmac-sha1')
-        self.assertEqual(ne.inMACType, 'hmac-sha1')
+        self.assertEqual(ne.outCipType, b'aes256-ctr')
+        self.assertEqual(ne.inCipType, b'aes256-ctr')
+        self.assertEqual(ne.outMACType, b'hmac-sha1')
+        self.assertEqual(ne.inMACType, b'hmac-sha1')
 
 
     def test_notImplementedClientMethods(self):
@@ -1725,7 +1732,7 @@
         # in data returned by self.transport.value()
         self.proto.dataReceived(self.transport.value())
 
-        self.assertEqual(common.MP(self.proto.x)[5:], '\x99' * 64)
+        self.assertEqual(common.MP(self.proto.x)[5:], b'\x99' * 64)
 
         # Data sent to server should be a transport.MSG_KEXDH_INIT
         # message containing our public key.
@@ -1738,7 +1745,7 @@
         KEXINIT messages requesting diffie-hellman-group14-sha1 result in
         KEXDH_INIT responses.
         """
-        self.assertKexInitResponseForDH('diffie-hellman-group14-sha1')
+        self.assertKexInitResponseForDH(b'diffie-hellman-group14-sha1')
 
 
     def test_KEXINIT_group1(self):
@@ -1746,7 +1753,7 @@
         KEXINIT messages requesting diffie-hellman-group1-sha1 result in
         KEXDH_INIT responses.
         """
-        self.assertKexInitResponseForDH('diffie-hellman-group1-sha1')
+        self.assertKexInitResponseForDH(b'diffie-hellman-group1-sha1')
 
 
     def test_KEXINIT_badKexAlg(self):
@@ -1755,8 +1762,8 @@
         KEXINIT message but doesn't have a key exchange algorithm that we
         understand.
         """
-        self.proto.supportedKeyExchanges = ['diffie-hellman-group2-sha1']
-        data = self.transport.value().replace('group1', 'group2')
+        self.proto.supportedKeyExchanges = [b'diffie-hellman-group2-sha1']
+        data = self.transport.value().replace(b'group1', b'group2')
         self.assertRaises(ConchError, self.proto.dataReceived, data)
 
 
@@ -1773,7 +1780,7 @@
         h.update(common.NS(self.proto.ourKexInitPayload) * 2)
         h.update(common.NS(self.blob))
         h.update(self.proto.e)
-        h.update('\x00\x00\x00\x01\x02') # f
+        h.update(b'\x00\x00\x00\x01\x02') # f
         h.update(sharedSecret)
         exchangeHash = h.digest()
 
@@ -1785,7 +1792,7 @@
         signature = self.privObj.sign(exchangeHash)
 
         d = self.proto.ssh_KEX_DH_GEX_GROUP(
-            (common.NS(self.blob) + '\x00\x00\x00\x01\x02' +
+            (common.NS(self.blob) + b'\x00\x00\x00\x01\x02' +
              common.NS(signature)))
         d.addCallback(_cbTestKEXDH_REPLY)
 
@@ -1796,14 +1803,14 @@
         """
         Test that _keySetup sets up the next encryption keys.
         """
-        self.proto.kexAlg = 'diffie-hellman-group1-sha1'
+        self.proto.kexAlg = b'diffie-hellman-group1-sha1'
         self.proto.nextEncryptions = MockCipher()
-        self.simulateKeyExchange('AB', 'CD')
-        self.assertEqual(self.proto.sessionID, 'CD')
-        self.simulateKeyExchange('AB', 'EF')
-        self.assertEqual(self.proto.sessionID, 'CD')
-        self.assertEqual(self.packets[-1], (transport.MSG_NEWKEYS, ''))
-        newKeys = [self.proto._getKey(c, 'AB', 'EF') for c in 'ABCDEF']
+        self.simulateKeyExchange(b'AB', b'CD')
+        self.assertEqual(self.proto.sessionID, b'CD')
+        self.simulateKeyExchange(b'AB', b'EF')
+        self.assertEqual(self.proto.sessionID, b'CD')
+        self.assertEqual(self.packets[-1], (transport.MSG_NEWKEYS, b''))
+        newKeys = [self.proto._getKey(c, b'AB', b'EF') for c in b'ABCDEF']
         self.assertEqual(self.proto.nextEncryptions.keys,
                           (newKeys[0], newKeys[2], newKeys[1], newKeys[3],
                            newKeys[4], newKeys[5]))
@@ -1821,25 +1828,25 @@
         self.proto.connectionSecure = stubConnectionSecure
 
         self.proto.nextEncryptions = transport.SSHCiphers(
-            'none', 'none', 'none', 'none')
-        self.simulateKeyExchange('AB', 'CD')
+            b'none', b'none', b'none', b'none')
+        self.simulateKeyExchange(b'AB', b'CD')
         self.assertIsNot(self.proto.currentEncryptions,
                          self.proto.nextEncryptions)
 
         self.proto.nextEncryptions = MockCipher()
-        self.proto.ssh_NEWKEYS('')
+        self.proto.ssh_NEWKEYS(b'')
         self.assertIs(self.proto.outgoingCompression, None)
         self.assertIs(self.proto.incomingCompression, None)
         self.assertIs(self.proto.currentEncryptions,
                       self.proto.nextEncryptions)
         self.assertTrue(secure[0])
-        self.proto.outgoingCompressionType = 'zlib'
-        self.simulateKeyExchange('AB', 'GH')
-        self.proto.ssh_NEWKEYS('')
+        self.proto.outgoingCompressionType = b'zlib'
+        self.simulateKeyExchange(b'AB', b'GH')
+        self.proto.ssh_NEWKEYS(b'')
         self.assertIsNot(self.proto.outgoingCompression, None)
-        self.proto.incomingCompressionType = 'zlib'
-        self.simulateKeyExchange('AB', 'IJ')
-        self.proto.ssh_NEWKEYS('')
+        self.proto.incomingCompressionType = b'zlib'
+        self.simulateKeyExchange(b'AB', b'IJ')
+        self.proto.ssh_NEWKEYS(b'')
         self.assertIsNot(self.proto.incomingCompression, None)
 
 
@@ -1848,7 +1855,7 @@
         Test that the SERVICE_ACCEPT packet starts the requested service.
         """
         self.proto.instance = MockService()
-        self.proto.ssh_SERVICE_ACCEPT('\x00\x00\x00\x0bMockService')
+        self.proto.ssh_SERVICE_ACCEPT(b'\x00\x00\x00\x0bMockService')
         self.assertTrue(self.proto.instance.started)
 
 
@@ -1858,7 +1865,7 @@
         """
         self.proto.requestService(MockService())
         self.assertEqual(self.packets, [(transport.MSG_SERVICE_REQUEST,
-                                         '\x00\x00\x00\x0bMockService')])
+                                         b'\x00\x00\x00\x0bMockService')])
 
 
     def test_disconnectKEXDH_REPLYBadSignature(self):
@@ -1866,7 +1873,7 @@
         Test that KEXDH_REPLY disconnects if the signature is bad.
         """
         self.test_KEXDH_REPLY()
-        self.proto._continueKEXDH_REPLY(None, self.blob, 3, "bad signature")
+        self.proto._continueKEXDH_REPLY(None, self.blob, 3, b"bad signature")
         self.checkDisconnected(transport.DISCONNECT_KEY_EXCHANGE_FAILED)
 
 
@@ -1874,7 +1881,7 @@
         """
         Test that NEWKEYS disconnects if it receives data.
         """
-        self.proto.ssh_NEWKEYS("bad packet")
+        self.proto.ssh_NEWKEYS(b"bad packet")
         self.checkDisconnected()
 
 
@@ -1884,7 +1891,7 @@
         differet from the asked-for protocol.
         """
         self.proto.instance = MockService()
-        self.proto.ssh_SERVICE_ACCEPT('\x00\x00\x00\x03bad')
+        self.proto.ssh_SERVICE_ACCEPT(b'\x00\x00\x00\x03bad')
         self.checkDisconnected()
 
 
@@ -1895,7 +1902,7 @@
         name of the service.
         """
         self.proto.instance = MockService()
-        self.proto.ssh_SERVICE_ACCEPT('') # no payload
+        self.proto.ssh_SERVICE_ACCEPT(b'') # no payload
         self.assertTrue(self.proto.instance.started)
         self.assertEqual(len(self.packets), 0) # not disconnected
 
@@ -1916,7 +1923,7 @@
         # The response will include our advertised group sizes.
         self.assertEqual(self.packets, [(
             transport.MSG_KEX_DH_GEX_REQUEST,
-            '\x00\x00\x04\x00\x00\x00\x08\x00\x00\x00\x20\x00')])
+            b'\x00\x00\x04\x00\x00\x00\x08\x00\x00\x00\x20\x00')])
 
 
     def test_KEX_DH_GEX_GROUP(self):
@@ -1926,10 +1933,10 @@
         """
         self.test_KEXINIT_groupexchange()
         self.proto.ssh_KEX_DH_GEX_GROUP(
-            '\x00\x00\x00\x01\x0f\x00\x00\x00\x01\x02')
+            b'\x00\x00\x00\x01\x0f\x00\x00\x00\x01\x02')
         self.assertEqual(self.proto.p, 15)
         self.assertEqual(self.proto.g, 2)
-        self.assertEqual(common.MP(self.proto.x)[5:], '\x99' * 40)
+        self.assertEqual(common.MP(self.proto.x)[5:], b'\x99' * 40)
         self.assertEqual(self.proto.e,
                           common.MP(pow(2, self.proto.x, 15)))
         self.assertEqual(self.packets[1:], [(transport.MSG_KEX_DH_GEX_INIT,
@@ -1948,10 +1955,10 @@
         h.update(common.NS(self.proto.ourKexInitPayload) * 2)
         h.update(common.NS(self.blob))
         # Here is the wire format for advertised min, pref and max DH sizes.
-        h.update('\x00\x00\x04\x00\x00\x00\x08\x00\x00\x00\x20\x00')
-        h.update('\x00\x00\x00\x01\x0f\x00\x00\x00\x01\x02')
+        h.update(b'\x00\x00\x04\x00\x00\x00\x08\x00\x00\x00\x20\x00')
+        h.update(b'\x00\x00\x00\x01\x0f\x00\x00\x00\x01\x02')
         h.update(self.proto.e)
-        h.update('\x00\x00\x00\x01\x03') # f
+        h.update(b'\x00\x00\x00\x01\x03') # f
         h.update(sharedSecret)
         exchangeHash = h.digest()
 
@@ -1964,7 +1971,7 @@
 
         d = self.proto.ssh_KEX_DH_GEX_REPLY(
             common.NS(self.blob) +
-            '\x00\x00\x00\x01\x03' +
+            b'\x00\x00\x00\x01\x03' +
             common.NS(signature))
         d.addCallback(_cbTestKEX_DH_GEX_REPLY)
         return d
@@ -1975,7 +1982,7 @@
         Test that KEX_DH_GEX_REPLY disconnects if the signature is bad.
         """
         self.test_KEX_DH_GEX_REPLY()
-        self.proto._continueGEX_REPLY(None, self.blob, 3, "bad signature")
+        self.proto._continueGEX_REPLY(None, self.blob, 3, b"bad signature")
         self.checkDisconnected(transport.DISCONNECT_KEY_EXCHANGE_FAILED)
 
 
@@ -2005,6 +2012,7 @@
     if dependencySkip:
         skip = dependencySkip
 
+
     def setUp(self):
         self.ciphers = transport.SSHCiphers(b'A', b'B', b'C', b'D')
 
@@ -2043,7 +2051,7 @@
 
         params = self.ciphers._getMAC(hmacName, secret)
 
-        key = secret[:digestSize] + '\x00' * blockPadSize
+        key = secret[:digestSize] + b'\x00' * blockPadSize
         innerPad = b''.join(chr(ord(b) ^ 0x36) for b in key)
         outerPad = b''.join(chr(ord(b) ^ 0x5c) for b in key)
         self.assertEqual(
@@ -2113,26 +2121,27 @@
     if dependencySkip:
         skip = dependencySkip
 
+
     def test_init(self):
         """
         Test that the initializer sets up the SSHCiphers object.
         """
-        ciphers = transport.SSHCiphers('A', 'B', 'C', 'D')
-        self.assertEqual(ciphers.outCipType, 'A')
-        self.assertEqual(ciphers.inCipType, 'B')
-        self.assertEqual(ciphers.outMACType, 'C')
-        self.assertEqual(ciphers.inMACType, 'D')
+        ciphers = transport.SSHCiphers(b'A', b'B', b'C', b'D')
+        self.assertEqual(ciphers.outCipType, b'A')
+        self.assertEqual(ciphers.inCipType, b'B')
+        self.assertEqual(ciphers.outMACType, b'C')
+        self.assertEqual(ciphers.inMACType, b'D')
 
 
     def test_getCipher(self):
         """
         Test that the _getCipher method returns the correct cipher.
         """
-        ciphers = transport.SSHCiphers('A', 'B', 'C', 'D')
-        iv = key = '\x00' * 16
+        ciphers = transport.SSHCiphers(b'A', b'B', b'C', b'D')
+        iv = key = b'\x00' * 16
         for cipName, (algClass, keySize, counter) in ciphers.cipherMap.items():
             cip = ciphers._getCipher(cipName, iv, key)
-            if cipName == 'none':
+            if cipName == b'none':
                 self.assertIsInstance(cip, transport._DummyCipher)
             else:
                 self.assertIsInstance(cip.algorithm, algClass)
@@ -2142,15 +2151,17 @@
         """
         Test that setKeys sets up the ciphers.
         """
-        key = '\x00' * 64
+        key = b'\x00' * 64
         for cipName in transport.SSHTransportBase.supportedCiphers:
             modName, keySize, counter = transport.SSHCiphers.cipherMap[cipName]
-            encCipher = transport.SSHCiphers(cipName, 'none', 'none', 'none')
-            decCipher = transport.SSHCiphers('none', cipName, 'none', 'none')
+            encCipher = transport.SSHCiphers(cipName, b'none', b'none',
+                                             b'none')
+            decCipher = transport.SSHCiphers(b'none', cipName, b'none',
+                                             b'none')
             cip = encCipher._getCipher(cipName, key, key)
             bs = cip.algorithm.block_size // 8
-            encCipher.setKeys(key, key, '', '', '', '')
-            decCipher.setKeys('', '', key, key, '', '')
+            encCipher.setKeys(key, key, b'', b'', b'', b'')
+            decCipher.setKeys(b'', b'', key, key, b'', b'')
             self.assertEqual(encCipher.encBlockSize, bs)
             self.assertEqual(decCipher.decBlockSize, bs)
             encryptor = cip.encryptor()
@@ -2166,12 +2177,12 @@
         """
         Test that setKeys sets up the MACs.
         """
-        key = '\x00' * 64
+        key = b'\x00' * 64
         for macName, mod in transport.SSHCiphers.macMap.items():
-            outMac = transport.SSHCiphers('none', 'none', macName, 'none')
-            inMac = transport.SSHCiphers('none', 'none', 'none', macName)
-            outMac.setKeys('', '', '', '', key, '')
-            inMac.setKeys('', '', '', '', '', key)
+            outMac = transport.SSHCiphers(b'none', b'none', macName, b'none')
+            inMac = transport.SSHCiphers(b'none', b'none', b'none', macName)
+            outMac.setKeys(b'', b'', b'', b'', key, b'')
+            inMac.setKeys(b'', b'', b'', b'', b'', key)
             if mod:
                 ds = mod().digest_size
             else:
@@ -2181,11 +2192,11 @@
                 mod, i, o, ds = outMac._getMAC(macName, key)
             seqid = 0
             data = key
-            packet = '\x00' * 4 + key
+            packet = b'\x00' * 4 + key
             if mod:
                 mac = mod(o + mod(i + packet).digest()).digest()
             else:
-                mac = ''
+                mac = b''
             self.assertEqual(outMac.makeMAC(seqid, data), mac)
             self.assertTrue(inMac.verify(seqid, data, mac))
 
@@ -2206,12 +2217,13 @@
             ]
 
         for key, data, mac in vectors:
-            outMAC = transport.SSHCiphers('none', 'none', 'hmac-md5', 'none')
-            outMAC.outMAC = outMAC._getMAC("hmac-md5", key)
+            outMAC = transport.SSHCiphers(b'none', b'none', b'hmac-md5',
+                                          b'none')
+            outMAC.outMAC = outMAC._getMAC(b"hmac-md5", key)
             (seqid,) = struct.unpack('>L', data[:4])
             shortened = data[4:]
             self.assertEqual(
-                mac, outMAC.makeMAC(seqid, shortened).encode("hex"),
+                mac, binascii.hexlify(outMAC.makeMAC(seqid, shortened)),
                 "Failed HMAC test vector; key=%r data=%r" % (key, data))
 
 
@@ -2223,6 +2235,7 @@
     if dependencySkip:
         skip = dependencySkip
 
+
     def _runClientServer(self, mod):
         """
         Run an async client and server, modifying each using the mod function
@@ -2255,14 +2268,14 @@
             self.assertEqual(client.errors, [])
             self.assertEqual(server.errors, [(
                         transport.DISCONNECT_CONNECTION_LOST,
-                        "user closed connection")])
-            if server.supportedCiphers[0] == 'none':
+                        b"user closed connection")])
+            if server.supportedCiphers[0] == b'none':
                 self.assertFalse(server.isEncrypted(), name)
                 self.assertFalse(client.isEncrypted(), name)
             else:
                 self.assertTrue(server.isEncrypted(), name)
                 self.assertTrue(client.isEncrypted(), name)
-            if server.supportedMACs[0] == 'none':
+            if server.supportedMACs[0] == b'none':
                 self.assertFalse(server.isVerified(), name)
                 self.assertFalse(client.isVerified(), name)
             else:
@@ -2280,7 +2293,7 @@
         the various combinations of ciphers.
         """
         deferreds = []
-        for cipher in transport.SSHTransportBase.supportedCiphers + ['none']:
+        for cipher in transport.SSHTransportBase.supportedCiphers + [b'none']:
             def setCipher(proto):
                 proto.supportedCiphers = [cipher]
                 return proto
@@ -2293,7 +2306,7 @@
         Like test_ciphers, but for the various MACs.
         """
         deferreds = []
-        for mac in transport.SSHTransportBase.supportedMACs + ['none']:
+        for mac in transport.SSHTransportBase.supportedMACs + [b'none']:
             def setMAC(proto):
                 proto.supportedMACs = [mac]
                 return proto
@@ -2327,6 +2340,7 @@
         return defer.DeferredList(deferreds, fireOnOneErrback=True)
 
 
+
 class RandomNumberTests(unittest.TestCase):
     """
     Tests for the random number generator L{_getRandomNumber} and private
@@ -2335,6 +2349,7 @@
     if dependencySkip:
         skip = dependencySkip
 
+
     def test_usesSuppliedRandomFunction(self):
         """
         L{_getRandomNumber} returns an integer constructed directly from the