A Novel Key-Based Transposition Scheme for Text Encryption

Crypt21 is designed in this paper, a block cipher which uses classical substitution whereas a new transposition scheme. The transposition scheme proposed is entirely dependent on key and induces security by having substitution and transposition both dependant on key. The design is iterative and can be extended to many rounds. Strengths include that it is safe from frequency analysis and dependant on original key in many ways. Weaknesses include possibilities of related key attacks due to weak key schedule. A text based implementation is done and working is explained via example in this paper. Implementation is done in MATLAB. Further directions to make this idea more practical are also proposed in this paper.