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I'm not an expert, but as far as I understand that would be impossible. My reasoning follows. In the case of encryption - even if an attacker guesses correctly - he doesn't know that. So secrecy can be perfect. With integrity, on the other hand, even if an attacker doesn't know he guessed correctly, the attacked will be fooled into believing the integrity ...


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Yes, there is the one-time MAC. This is a scheme which ensures that an adversary (even one with infinite computational resources) has a negligible chance of altering the message or forging a fake message without detection. Edit to add: Mikero's comment and the other answer demonstrate that we need to be clear about what we mean by "perfect" integrity. "...


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As fgrieu noted in his answer using sign-then-encrypt is probably the best way of handling encrypted & signed messages. However when the OpenPGP format in RFC 4880 is studied it seems that it uses both PKCS#1 v1.5 padding and CBC mode encryption. Both schemes are vulnerable to padding oracle attacks. So it is important to make sure the software is not ...


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Yes, PGP's sketch as in the question is sound by today's textbooks on cryptography, and reasonable from a computer security standpoint. Applying digital signature then encryption (critically: including on the signature) does provide data integrity and confidentiality for the message. PGP's way of doing things has the characteristic that one able to decipher ...


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and encryption does not provide data integrity. You might want to read up on authenticated encryption. However, even if that isn't used it's still not a big problem for if an attacker corrupts the encrypted text the cleartext produced the by corrupted ciphertext cannot be authenticated, i.e. the signature will be corrupted or the hashes won't be equal.



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