Abstract
Due to the prevalent use of internet-enabled devices, confidentiality and privacy in communication has been more important than ever. Encryption algorithms, such as AES and RSA, are used to ensure the security and privacy of such communications. However, as computers get computationally powerful, more complex encryption algorithms are needed to avoid brute force attacks. This complexity in the algorithms also means that encryption and decryption of messages using these algorithms can be slow. To avoid this decrease in speed, many optimizations have been proposed to make these complex algorithms perform much faster. Emilia Käsper and Peter Schwabe proposed one such optimization to AES in their paper “Faster and Timing-Attack Resistant AES-GCM.” They describe a fast constant-time AES encryption algorithm, which is also immune from cache-timing attacks, using Intel’s SSE instructions. This paper focuses on the study of Käsper and Schwabe’s proposal and implements a fast constant-time AES decryption algorithm that can work with their encryption algorithm. The paper concludes that while the decryption algorithm is slower than the encryption algorithm proposed by Käsper and Schwabe, it is about 3 times faster than the standard decryption implementation such as OpenSSL. Therefore, this fast decryption algorithm paired with Käsper and Schwabe’s fast encryption algorithm can provide users a complete AES package that can be used in applications that require fast encryptions and decryption along with protection against timing attacks.