[E-Lang] Combining strong authentication and secrecy protocols.
Tue, 20 Feb 2001 17:46:31 +0000
> Ben writes:
> > The actual algorithm is to XOR all the plaintext blocks together, and
> > use that in place of the last plaintext block. The last block should
> > include a checksum. Hence, any change to the plaintext anywhere will
> > corrupt the last block and invalidate the checksum.
> Just be careful with these xor based checkums that you don't try to
> use them with an xor based stream cipher like RC4! That was one of the
> main factors in the break of the wireless protocol by a group including
> David Wagner. The attacker can xor into the ciphertext and it will go
> through as a corresponding xor to the plaintext; he can then compensate
> by xoring the checksum and the change won't be noticed.
Yes, a good example of how naive combination of various secure
components does not necessarily result in a secure whole.
"There is no limit to what a man can do or how far he can go if he
doesn't mind who gets the credit." - Robert Woodruff