DES Cryptanalysis

[Kevin L Prigge]

I'm looking for pointers, or perhaps an explanation of the statement
I found in Applied Cryptography (section 9.6) where it implies
that if the IV is not unique in CFB mode, the cryptanalyst can recover the
plaintext.

The reason that this interests me is that I have a file, encrypted
with DES in CFB mode. I believe I know the first 8 bytes of plaintext
and I also know the IV used. While it'd be nice to decrypt this
file, I don't know that it'd be worth brute forcing the key, even if
the spare cycles to do it were available. Any pointers to any pertinant
information would be appreciated. Thanks. 


-- 
Kevin L. Prigge        |"A computer lets you make more mistakes faster 
UofM Central Computing | than any invention in human history--with the 
email: klp at umn.edu     | possible exceptions of handguns and tequila."
01001001110101100110001| - Mitch Ratcliffe