aes - What is the use of Additional data or associated ... …

aes - What is the use of Additional data or associated ...

• The algorithms are designed to detect tampering with encrypted data, ensuring the receiver receives the intended message from the sender.

• An authentication tag, derived from the ciphertext, verifies message integrity; any modification by an attacker will likely result in a mismatched tag, causing message rejection.

• Additional Authenticated Data (AAD) mitigates the risk of replay attacks, where an attacker could resend a message in a different context to mislead the recipient.

• AAD allows the sender to define the message context during encryption, ensuring that the receiver can only decrypt messages meant for that specific context.

• If the AAD used during encryption does not match the expected AAD by the receiver, the tags will not align, leading to message rejection.

• AAD can consist of any identifying string, such as a serial number or a question related to a response, providing context for the encrypted message.

• In cases where only a single message is encrypted with a key, AAD can be omitted, as its additional security may not be necessary.

• The authentication process's effectiveness depends on assumptions, including that the attacker does not know the AES key, that AES is secure, and that the attacker has not observed two valid ciphertexts with the same nonce.