A Study on the Processing and Reinforcement of Message Digest Through Two-Dimensional Array Masking

Hash algorithms have been widely used for cryptography. It has been impossible to decrypt the ciphertexts generated through hash algorithms, as an operation that damages the original text is performed. The vulnerability of SHA1 (an old hash algorithm) has been revealed, and there has been a great deal of data available for dictionary attacks. Although the industry has been gradually refraining from using SHA1, it remains in use in some existing systems for various reasons. In particular, when problems resulting from medical service interruption or mass update are directly related to a person's life, updating the encryption algorithm can be a burden. In this study, we aim to increase the complexity of ciphertexts by postprocessing hash ciphertext by masking message digest to a two-dimensional array constructed using an image processing technique. This will allow the use of hash ciphertexts with increased complexity in some medical devices that are forced to use old hash algorithms for various reasons.