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In general the AAD itself is not required or won't change the security of the GCM mode of operation itself. It may however directly influence the security of the protocol in which GCM is deployed. For instance, you may have specific configurable parameters outside the ciphertext itself. These parameters may very well include: version number of the ...


AAD has nothing to do with making it "more secure". The aim of AAD is to attach information to the ciphertext that is not encrypted, but is bound to the ciphertext in the sense that it cannot be changed or separated. (Conceptually, the MAC is computed over the AAD and the ciphertext together.)


Generally speaking, using proprietary encryption is a major problem, because the algorithms which are used are not subject to the same amount of review they would be if public. But it is possible to gain some advantages this way, by taking advantage of public knowledge. Maurer & Massey (1993) prove that a cascade of ciphers with independent keys is at ...

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