Xenix & crypt

[Landon Noll]

In article <321 at petrus.UUCP> karn at petrus.UUCP writes:
 >If DES is so sensitive, then why was the algorithm published in
 >the Federal Register?  How about all of the books that have been written
 >on cryptography in the past ten years that include sections on DES?

Even more stupid is how easy it is to mung the international version of
crypt(3).  Login still uses crypt(3), but only to ENCRYPT, not decrypt.
Anyone who does a diff of the US crypt(3) and the "US-international"
crypt(3) will find only 3 major types of changes.  Do a simple diff
of the two versions and see for yourself.  It would not be too hard
to mung crypt(3) source if you only had the international version.

Any binary user can, with a bit of thought, form decrypt(3) from crypt(3).
Look at the DES as noted in the Fed. register.  Notice that there is a
16 strange encryption going on.  Now since they removed the encrypt/decrypt
flag from the encrypt(3) routine (diff the old and new crypt(3) man pages)
one might guess that encrypt(3) itself needs to be munged.  Take your
friendly dis-asm prog (use adb, or whatever...) and try to find this
16 stage loop.  Adjust the loop so that it starts at the high value
and steps in the reverse direction.  You now have encrypt doing a decryption.

Of course, if a binary user has the Fed. register, they might as well
write a routine for it!  But some folks might want to form their own
binary version of decrypt(3) just out of spite.  :-)

chongo <try RSA> /\oo/\
-- 
no comment is a comment.