Re: how to detect breakage -- lures etc.??

--===============8182092532604922261==
Content-Type: multipart/alternative; boundary="00000000000092e3b0059b57bc93"

--00000000000092e3b0059b57bc93
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

n Sat, Jan 4, 2020 at 2:24 AM Arnold Reinhold via cryptography <
[email protected]> wrote:

>
> >  The SIGABA/ ECM-II sets, which by all accounts was never broken during
> the war,

In* Big Machines: Cryptographic Security of the German Enigma, Japanese
PURPLE, and US SIGABA/ECM Cipher Machines *Kelly states (IIRC) that in the
1970s, NSA deputy director Tordella (
https://en.wikipedia.org/wiki/Louis_W._Tordella) stated that they still
could not break SIGABA/ECM.

A paper by Stamp and Chan estimated that the SIGABA had a key of about 95
bits.  IIRC, they assume that the attacker knows the rotors.  If you assume
that the attacker has to recover the rotors from observing the traffic,
then the work required must be much greater.

> * five rotors in the alphabet maze, chosen from a set of ten
> * pseudo random stepping of the five rotors, at first controlled by an
> additional set of rotors
> * no reflector, eliminating the =E2=80=9Cno letter can encode to itself=
=E2=80=9D weakness,
> at the expense of a bulky 26+ position encrypt/decrypt switch
>
> The rotors in the SIGAGA were reversible---adding another 2^10 bits to th=
e
key.  The US issued new  rotors every year.  If the Germans had done that
with Enigma, the allies would have had a much harder time recovering
Enigma-coded message.

Chuck

--00000000000092e3b0059b57bc93
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail=
_attr">n Sat, Jan 4, 2020 at 2:24 AM Arnold Reinhold via cryptography &lt;<=
a href=3D"mailto:[email protected]">[email protected]</a>&g=
t; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0p=
x 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
&gt;=C2=A0 The SIGABA/ ECM-II sets, which by all accounts was never broken =
during the war, </blockquote><div><div style=3D"font-size:small" class=3D"g=
mail_default">In<i> Big Machines: Cryptographic Security of the German Enig=
ma, Japanese PURPLE, and US SIGABA/ECM Cipher Machines </i>Kelly states (II=
RC) that in the 1970s, NSA deputy director Tordella (<a href=3D"https://en.=
wikipedia.org/wiki/Louis_W._Tordella">https://en.wikipedia.org/wiki/Louis_W=
._Tordella</a>) stated that they still could not break SIGABA/ECM.=C2=A0 <b=
r></div><div style=3D"font-size:small" class=3D"gmail_default"><br></div><d=
iv style=3D"font-size:small" class=3D"gmail_default">A paper by Stamp and C=
han estimated that the SIGABA had a key of about 95 bits.=C2=A0 IIRC, they =
assume that the attacker knows the rotors.=C2=A0 If you assume that the att=
acker has to recover the rotors from observing the traffic, then the work r=
equired must be much greater.<br></div></div><blockquote class=3D"gmail_quo=
te" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204=
);padding-left:1ex">
* five rotors in the alphabet maze, chosen from a set of ten<br>
* pseudo random stepping of the five rotors, at first controlled by an addi=
tional set of rotors<br>
* no reflector, eliminating the =E2=80=9Cno letter can encode to itself=E2=
=80=9D weakness, at the expense of a bulky 26+ position encrypt/decrypt swi=
tch <br>
<br></blockquote><div><div style=3D"font-size:small" class=3D"gmail_default=
">The rotors in the SIGAGA were reversible---adding another 2^10 bits to th=
e key.=C2=A0 The US issued new=C2=A0 rotors every year.=C2=A0 If the German=
s had done that with Enigma, the allies would have had a much harder time r=
ecovering Enigma-coded message.=C2=A0 <br></div></div><div><br></div><div><=
div style=3D"font-size:small" class=3D"gmail_default">Chuck</div></div></di=
v></div>

--00000000000092e3b0059b57bc93--

--===============8182092532604922261==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

_______________________________________________
The cryptography mailing list
[email protected]
https://www.metzdowd.com/mailman/listinfo/cryptography

--===============8182092532604922261==--