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> (to my knowledge) no standardized stream cipher that provides output feedback mode (OFB) out-of-the-box. I wasn't aware stream ciphers typically had differen
by 0xdeadb00f 5y ago
> (to my knowledge) no standardized stream cipher that provides output feedback mode (OFB) out-of-the-box.
I wasn't aware stream ciphers typically had different modes of operation like block ciphers did. Could you expand on this? I'm kind of interested.
- ThePhysicist 5y agoOFB means you feed the output of the cipher back to the input. Hence if you have two character sequences that share a prefix e.g. "abc123" and "abcxyz" the first three cipher stream bits will be identical and then deviate based on the feedback the cipher gets (assuming no IV and identical key). This is interesting for pseudonymization when you want to e.g. create cryptographically secure pseudonyms that preserve prefixes (think IP address pseudonyms that preserve subnet groupings).