The Authentication Encryption (AE) scheme based on the duplex construction cannot be parallelized at the algorithmic level. To be competitive with some block cipher based modes like OCB (O set CodeBook) or GCM (Galois Counter Mode), a scheme should allow parallel processing. In this paper the authors show how parallel AE can be realized within the framework provided by the duplex construction. The first variant, pointed by the duplex designers, is a tree-like structure. Then they simplify the scheme replacing the final node by the bitwise xor operation and show that such a scheme has the same security level.