DAA is one of the implementations of #Message Authentication Code (MAC) defined by FIPS PUB 113 and ANSI X9.17 which is based on Cipher Block Chaining (CBC)#. The initialisation value (IV) used is 0 and the final block is padded by 0s, which is where the MAC derived from. If the final block is too big, it will use the left most \(M\) (\(16 \le M \le 64\)) bits of the final block as the MAC.
The key and MAC sizes are too small to be considered secure though.