A hybrid cryptosystem based on zig-zag algorithm and Rivest Shamir Adleman (RSA) algorithm

The security issue is one of the most critical aspects of the message. Cryptography is a science based on a mathematical technique for security-related information with confidentiality, data integrity, and authentication. A hybrid cryptosystem works by combining symmetric and asymmetric algorithms. The purpose of using zig – zag algorithm and RSA algorithm is to cover the weakness of symmetric and asymmetric algorithm. Zig-zag Cipher is one of the classical cryptographic algorithms that use the technique of transposition. The method of inversion is utilizing the character permutation. The RSA algorithm is an asymmetric cryptographic algorithm that has used most frequently, and this is due to the reliability. The length of RSA keys in bits can be set, with the longer the bits, the more difficult to solve because of the difficulty of factoring the two huge numbers, but this has an impact on the more extended the decryption process. This research used to encrypt the message by zig-zag algorithm while the RSA algorithm encrypts the key of the zig-zag algorithm. The results of this research are the bigger size of the file, then the higher the size of the ciphertext. Based on the graph of the plaintext length against the processing time obtained the results of the length of the plaintext is directly proportional to the time and form of the linear graph. Encryption and decryption processes require different time durations. The encryption process takes longer time than decryption process. (paper)