An efficient scheme of authenticated encryption with associated data

An efficient scheme of authenticated encryption with associated data is provided by combining a collision resistant hash function with an authenticated encryption scheme. The hash function is used to compress an arbitrary length header to a fixed length nounce. The authenticated encryption scheme is the improvement of OCB mode of operation. OCB is believed to provide extremely high protection with encryption and message authentication in a most efficient way. However, when OCB mode of operation is used to handle large amount of data, it is easy to find collision so that the mode will lose the authenticity capability with probability one. An improved scheme on the checksum is proposed to avoid the existing collision attacks efficiently. The random element without additional complicated calculation is introduced to translate the segment plaintexts in the checksum. At last, the security of the scheme of authenticated encryption with associated data is analyzed.