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As correctly pointed out in a comment, the authenticated encryption model assumes that the attacker knows the algorithm; the attacker can query the encryption oracle with any plaintext $P$ (and a unique nonce $N$) and get MAC-then-Encrypt ciphertext $C$; the attacker can query the decryption oracle with any string $C$ pretending to be a ciphertext. No ...


2

If there exists an encryption scheme, then there exists an encryption schemes such that one can easily modify a single ciphertext so that whether or not that modifies the decryption result depends in a predictable-and-useful way on what the plaintext message was, such as: The modified encryption operation outputs a zero concatenated with the original ...


4

It has the disadvantages of any MAC-then-encrypt scheme, which I'm quoting from the linked answer below. In addition: It has the property that you need both a nonce and a hash, so for equivalent security it requires more message space. The nonce has to be random, so it requires strong random numbers for each message, unlike e.g. AES CTR + HMAC. Doesn't ...


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I haven't seen much analysis on using ordinary hashes for content authentication. Can anyone can give me a pointer on whether this is safe? With good choice of primitives it is. Public key signatures use a hash function in a similar way to identify the message signed. However, where a MAC only needs what amounts to second preimage resistance, a hash ...


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No. RSA-OAEP is indistinguishable under adaptive chosen cipher text attacks (and even non malleable under adaptive chosen cipher text attacks), but it is not an instance of authenticated encryption. - The sender who encrypts the message might even be anonymous to the recipient who decrypts the message. More generally, in a successful Chosen Cipher text ...


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No, CCA does not imply authenticated encryption. CCA tries to recover the secret using chosen ciphertexts. A well designed block cipher should in itself already process the property that the key cannot be retrieved. If used with a properly implemented block mode of operation, this property should hold. Using authenticated encryption a CCA attack should not ...


4

Before answering your questions: GCM is an authentication encryption mode of operation, it is composed by two separate functions: one for encryption (AES-CTR) and one for authentication (GMAC). It receives as input: a Key a unique IV Data to be processed only with authentication (associated data) Data to be processed by encryption and authentication It ...



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