Authenticated Encryption (AE) is a very important technique that ensures the security of data transportation. AE combines encryption and authentication to provide both privacy and authenticity of the data. In this paper, design, analysis and simulation of a fast and new Authenticated Encryption architecture called Authenticated Encryption SSEA3 (AESSEA3) is introduced on the basis of unpredictability concept. Unpredictability is a concept based on dynamic use of encryption algorithms, where instead of using single encryption algorithm for producing the ciphertext, multiple encryption algorithms are used in the same structure. Pseudo Random Number Generator (PRNG) is used to select which encryption algorithm will be used. Two double AES-256 are used with only 3 rounds to add the unpredictability concept which provide high speed and high security level. The plaintext enters one Double AES-256 and RC4 output enters the other Double AES-256. Also, the security increased by Xoring between the two outputs from the two algorithms to get the ciphertext. The proposed algorithm is faster than AGEIS which is one of the fastest AE algorithms. A new structure for AE is introduced to confirm authenticity. Tag partitioning concept is used. The proposed algorithm can resist different types of
cryptanalysis attacks.