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A comment on The Cryptographic Doom Principle.

Re:The Cryptographic Doom Principle by diafygi on Saturday January 10, 2015 @08:24AM (#8866709)
What does OpenPGP do? If you have the MAC in plaintext, wouldn't anyone be able to determine who encrypted the message?
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Re:The Cryptographic Doom Principle by maxerickson on Saturday January 10, 2015 @09:06AM (#8866768)
It calls it a modification detection code, but it does "Authenticate Then Encrypt":

https://tools.ietf.org/html/rfc4880#section-5.13

It also does digital signatures (but those are different than a MAC, they verify the identity of the sender).

The MAC takes a shared secret as input, so it should only reveal anything to parties that possess that secret.

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