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Date: Fri, 20 Jun 2008 12:59:34 +0200
From: "Samuel Moñux" <>
Subject: NetscreenOS passwords

Hello everyone,

I have made a little patch for auditing Netscreen OS passwords. It's not
very efficient and probably doesn't meet the code quality standards of John
the ripper's, but it may be of help to someone, or the seed for a better
implementation. I haven't tested it on big endian machines so probably it's
not endian-safe.

I became intrigued about the format of Netscreen passwords, since it was
undocumented, and had clear signs of obfuscation. I did my research
decompiling a Java application called NSM (Netscreen Security Manager).
Since the bytecode files were not obfuscated, it was very easy to find how
the password was generated. After doing this, I found that someone had
already done it the hard way[1], but without publishing his "John the
ripper" patch, which seemed an interesting exercise.

NetscreenOS passwords are basically raw MD5, where the username and a
constant string(":Administration Tools:") are used as the salt. The 128 bits
MD5 hash is mapped to characters in the range [A-Za-z0-9+/] in a weird
manner: every 16 bits word is splitted in 3 parts of 4bits, 6bits and 6bits.
These parts are used as indexes in an array which contains every character
in that range.

After that, a further obfuscation is performed. The characters of the string
"nrcstn"(netscreen without the vowels and reversed) are interpolated in
certain positions. The final password looks like this:

As I said, I hope it may be of help to someone. It was fun to do the
research and the coding.

Best regards,


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