The FPGA encryption system uses the AES-GCM (Advanced Encryption Standard - Galois/Counter Mode) authenticated encryption algorithm. The AES-GCM standard is an official standard supported by the National Institute of Standards and Technology (NIST) and the U.S. Department of Commerce (http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf). An advantage of the AES-GCM algorithm is that it also supports built-in authentication.
The FPGA AES encryption system uses a 256-bit encryption key to encrypt or decrypt blocks of 128 bits of data at a time. According to NIST, there are 1.1 x 1077 possible key combinations for a 256-bit key.
Symmetric encryption algorithms such as the AES algorithm use the same key for encryption and decryption. The security of the data is therefore dependent on the secrecy of the key.