ATM CELL ENCRYPTION AND KEY UPDATE SYNCHRONIZATION

This paper presents a data compaction/randomization based approach as a mode of block encryption for ATM (Asynchronous Transfer Mode) cells. The presented approach converts a plaintext into pseudo-random plaint ext before ciphering to conceal patterns in the plaintext. The underly ing idea behind this scheme is the Shannon's principles of ''confusion '' and ''diffusion'' which involve breaking dependencies and introduci ng as much randomness as possible into the ciphertext. In this scheme, confusion and diffusion are introduced into the system by first compr essing the ATM cell payload and then spreading a continuously changing random data over the entire content of the cell. As a mode of operati on for block ciphering, this scheme offers the following attractive fe atures: (i) plaintext patterns are pseudo-randomized and chained with ciphertext (thereby, preventing against ''dictionary'', ''known plaint ext'', and ''statistical analysis'' attacks), (ii) it is self-synchron izing, (iii) cell loss has no additional negative effect, (iv) no IV ( Initialization Vector) storage is required, (v) it is encryption-algor ithm independent, (vi) there is no cell-to-cell dependency (no feedbac k from previous cells), and (vii) it is highly scalable (i.e., cells f rom the same stream can be ciphered and deciphered in parallel). This paper also presents a secure mechanism for in-band synchronization of encryption/decryption key updates using a ''marker-cell'' that is carr ied within the data channel. An important aspect of both the above mec hanisms is that they do not require any changes to the ATM cell header or ATM infrastructure.