Hi all, (Apologies for asking two questions in quick succession on this mailing list: they were similar but distinct so I thought I should put two posts up. As before, any help is greatly appreciated).
The software I'm writing sends an encrypted file to a peer for safe keeping (for data backup purposes). The peer never needs to decrypt the file - only the sender knows the key. The peer also is sent metadata about the file for later recovery. My question is this: is there any harm in sending, in plaintext, the hash of the *original* plaintext file to the peer? This would be used when recovering the file to make sure it has been safely decrypted etc. Assume the hash would be cryptographically secure (i.e. SHA256). Could that information be realistically used to attack the encrypted data? i.e., you have the encrypted file, you have the hash of what the plaintext would be. Does this benefit an attacker, and if so how much? (I realise that there is an obvious solution here which is to simply encrypt the hash when I send it to the peer, but just for reasons of legacy code, it would be easier to send the hash plain text; for the sake of argument, please assume I'd prefer not to do this). Thanks again, John _______________________________________________ FDE mailing list [email protected] http://www.xml-dev.com/mailman/listinfo/fde
