4 ms·
It's still very unclear (having spent a few minutes on the RFC) what it does exactly. It sounds like a mechanism to detect accidental errors (say, user copy-pas
by gnull 4y ago
It's still very unclear (having spent a few minutes on the RFC) what it does exactly. It sounds like a mechanism to detect accidental errors (say, user copy-pasting encrypted data incorrectly or passing some garbage in place of ciphertext) and not maliciously crafted modifications. More like error correcting code than authentication.
The fact that it detects one byte being modified means nothing.
- upofadown 4y agoIn the case of pass, no authentication is normally done, so what remains has to be an integrity check. Pass can sign git commits, but OpenPGP signs the content directly, so the MDC is not used. The encryption mode normally used in OpenPGP is an improved version of cipher feedback (OCFB) for the block mode and something called the modification detection code (MDC) to detect modification. The two (OCFB-MDC) work together to produce an authenticated encryption mode based on shared knowledge of the symmetrical encryption key. In practice few seem to bother with the MDC but it is there and is cryptographically strong should an implementer want to use it for preventing, say, EFAIL.