Enhancement of Security through an Efficient Substitution- based Block Cipher of Bit-level Implementation with Possible Lossless Compression

This paper presents a substitution-based block cipher that considers a file to be encrypted as a bit-stream. The cipher implements a storage efficient algorithm through which along with encryption a reduction in size is also achieved. As encryption is done at bit label, this algorithm can be implemented on any kind of files. A tendency of increase in execution time is observed. The proposed technique is compared with the existing International Data Encryption Algorithm (IDEA) with respect to execution time and degree of non-homogeneity. A generalized expression for the key space is formularized. Key Words: cryptography, encryption, decryption, cipher, private key, symmetric key, plain text, cryptographic modeling