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Date: Fri, 11 Oct 2013 21:47:51 +1100
From: Michael Samuel <>
Subject: otp-md5 format


I have some code that does otp-md5 calculations fairly fast (I did
2^47 in a week using an i7), including opencl and gcc vector versions
that I was looking of putting into a JtR format plugin.

I've taken a quick look at the code, but was hoping somebody could
give me some shortcuts.  I saw the wiki page on writing formats, but
it seemed to only has a vague reference to the format plugin api
(which is what you want now, right?)

First, is there a salted hash format that I could hollow out and reuse
fairly easily?

Second, I added to md5.c an alternative MD5Final that fills in 2
unsigned ints {a^c, b^d}, but I noticed in the header that there's a
#ifdef OPENSSL there - does that mean that the JtR md5 doesn't get
used if OpenSSL is linked in?

Finally, I wanted advice on how the password file entry should look.
The natural way for s/key would be an OTP extended response, eg
"otp-md5 sa12345 99", followed by the OTP in either hex or words (I
think I'd just do hex).  Since that seems unlike the rest of JtR, is
there any other suggestions?  The fields are: algorithm, salt,
sequence, otp.


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