AES ECB mode for both encryption and authentication Can AES ECB mode be used for both encryption and authentication, assuming the following conditions are always true?


Encryption of exactly 128-bit (1 block) size messages
Different keys used for both encryption and authentication
Authentication AES ECB uses encrypted ciphertext as input and outputs 128-bit MAC
[1] - For a single block, AES ECB is a secure MAC.

[2] - AES ECB encryption for a single block suffers from one of the problems that AES ECB suffers from in general, namely that it is deterministic. The same message encrypted with the same key results in the same ciphertext. How big of an issue is that for your application? Only you can answer that at the moment because we don't have the details of the application.

[1] - https://crypto.stackexchange.com/a/18947/706
[2] - https://crypto.stackexchange.com/a/8053/706