The Alma Technologies AES-GCM128 IP Core implements the GCM-AES authenticated encryption and decryption, as specified in the NIST SP800-38D recommendation for GCM and GMAC and the FIPS-197 Advanced Encryption Standard. The core can be programmed to encrypt or decrypt 128-bit blocks of data, using 128-, 192-, or 256-bit cipher-key. In addition, using the GHASH algorithm a Hash value - the TAG - is calculated for the encrypted, or the additional plaintext, data. Then, in decryption mode, the calculated TAG is compared with the TAG that accompanies the ciphertext data and a Fail or Pass flag is accordingly generated.