I did some researches about forgery attack and chosen-message attack.

For me, forgery attacks are more focused on the verifiability whereas chosen-message attacks are similar to brute-force attacks.

I am in the right way? If not, could you help me to understant better.

Thank you,

  • $\begingroup$ Do you mean mac forgery by forgery attack? $\endgroup$ – kelalaka Feb 8 at 13:31
  • $\begingroup$ I would like to know in general the difference between them? Do you have an idea? $\endgroup$ – lu13 Feb 8 at 13:44

The concepts, MAC forgery attack, and chosen plaintext attack (CPA) are a different type of attacks.

  1. In CPA attack the attacker asks for the encryption of messages. The aim of the attacker is revealing all or part of the key. There are two types

    • Batch CPA: In this attack, the attacker chooses the messages and get the results not adaptively, that is the list is fixed.

    • Adaptive CPA (CPA2): In this attack, the attacker can request additional ciphertext of plaintext after seeing some ciphertext. So, he adapts himself according to information.

  2. In mac message forgery, the aim is not the key. The attacker tries to forge a valid MAC for a message $m$ that the MAC of $m$ is never calculated before by a legitimate signer. The message can be plaintext or the attacker has CPA2 attack, i.e. the attacker has access to the system that can encrypt and calculate the MAC but never releases the key.


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