Enhanced counter mode

Abstract

There are plenty of modes of operation for block ciphers available. All of them are developed as ciphers' extension or enhancement tool to gain better security or additional features. NITS had defined 5 modes as the standards; they are ECB, CBC, CFB, OFB and CTR mode. Among these modes, the CTR mode is the one that capable to be fully parallelized and possess more security features. However the disadvantage in the implementation of CTR mode is the deviation of the counter value between the encryptor and decryptor. The synchronization of the counter value can be easily lost during delivery or transmission, hence affecting the integrity of the system. This paper proposed a method to eliminate the synchronization issue by calculating the initial counter value from the initial value. The new counter value is calculated using an algorithm comprises of the cipher algorithm and a hash algorithm. This new method introduce minimum overhead at the beginning of each encryption or decryption process. By using the enhanced version of CTR mode, the implementation has become simplified, while maintaining its attractive features of better security and its ability of parallel processing.