Simultaneous compression and encryption

Abstract

EFFICIENCY and SECURITY is usually an important issue in information communication. Source coding reduces the size of the file being transmitted and hence shortening the transmitting time. File encryption increases information security by making data unreadable to anyone except those possessing a decryption key. Traditionally, they are performed separately or one after another to reduce data volume while maintaining information security. However, the simultaneous compression and encryption has become a frequent topic. In this project, compression and encryption are performed simultaneously on plaintext files based on an entropy scheme, arithmetic coding. In this scheme, compression is performed by iterating a piecewise linear chaotic map reversely while encryption is achieved by altering the chaotic map model continuously based on a secret key. To further increase the security, the compressed sequence is masked by a pseudorandom keystream which is generated from an integer skew tent map. The compression ratio of the scheme is comparable to arithmetic coding. Security is enhanced by the having a two-level protection, which results in a high key and plaintext sensitivity.