Re: Re: Mac port & endianness

Thanks for the insights.

With the announcement of the Java port, I think what I might do (next  
I get a chance to hack on it) is to try building a native interface  
atop that, since Java is now a first-class language with respect to  
developing MacOS apps.

--bob

On Jun 13, 2005, at 5:27 PM, Frank Pilhofer wrote:

> On Mon, 13 Jun 2005 07:02:15 -0400, Nolan Eakins  
> <[email protected]> wrote:
>
>>
>> I've had similar issues, but I don't have a big endian machine to  
>> test
>> on though. I took a crack at it, but still didn't get it. I've been
>> meaning to look at it again, but I've been busy w/ some other work at
>> the moment. I'd be open to hearing any secrets that you uncover.
>>
>>
>
> IIRC, the implementation of the Blowfish algorithm expects big-endian
> integers as input, i.e., the "block" that you pass into the Encrypt  
> and
> Decrypt operations are intended to be 64bit, big-endian integers.
>
> Now, Password Safe does the Wrong Thing(*) by feeding little-endian
> integers into the Blowfish algorithm, without swapping the byte-order.
> So instead of "7 6 5 4 3 2 1 0", Blowfish gets "4 5 6 7 0 1 2 3". So,
> with respect to the algorithm, Password Safe swaps the byte order for
> all input and output data.
>
> To accomodate for this in a platform independent manner, you have  
> to swap
> the byteorder yourself, every time you pass data to or receive data  
> from
> the Blowfish engine.
>
> E.g., in Passord Gorilla, the computation of H(RND) looks like
>
> proc pwsafe::int::computeHRND {RND password} {
>     set temp $RND
>     append temp "\x00\x00"
>     append temp $password
>     set tempSalt [pwsafe::int::sha1isz $temp]
>
>     set engine [iblowfish::ecb \#auto $tempSalt]
>     set cipher [pwsafe::int::genderbender $RND]
>     for {set i 0} {$i < 1000} {incr i} {
>     set cipher [$engine encryptBlock $cipher]
>     }
>     itcl::delete object $engine
>
>     set temp [pwsafe::int::genderbender $cipher]
>     append temp "\x00\x00"
>     return [pwsafe::int::sha1isz $temp 1]
> }
>
> where the "genderbender" operation swaps the byte order of every 32  
> bit
> integer in the block.
>
> I've tested this on big-endian machines.
>
> Frank
>
> (*) You might not want to call it "wrong," maybe just "obfuscated." It
> certainly does not seem to be a security issue.
>
> -- 
> Frank Pilhofer, [email protected]
>
>
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