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7h
comment Is the encryption of a hash a good MAC?
@poncho But the receiver is increasing the counter/change IV, so when he tries to verify the forged MAC it will fail? I mean using a stream cipher like this would still be insanely impractical in many cases due to the fact that you have to manage this state (the counter) somehow, but I don't think the example really shows how to break it without breaking the encryption as well.
1d
comment Is the encryption of a hash a good MAC?
Forgive me if I'm wrong, but for that CTR example to work the counter must have not been increased and the nonce must not have changed, which would already break basic encryption anyway, right?
Jul
6
comment Using a Hash as a secure PRNG
So generally, the NIST wasn't quite sure, but they felt like doing some random stuff would make it more.. random? ;)
Jul
6
comment Using a Hash as a secure PRNG
Yeah but that makes like 2 additional lines, still nowhere near the NIST algorithm
Jul
6
comment Using a Hash as a secure PRNG
As for the flaw in idea 2: That is correct, thanks for pointing that out. As for addition of entropy, what about hash(state || new_seed)? The fixed-length output can also easily be fixed, that's not really a concern I'm afraid.