An apparatus for hash cryptography has a hardware structure that is capable of providing both secure hash algorithm (SHA)-1 hash calculation and SHA-256 hash calculation. The apparatus for hash cryptography generates a plurality of first message data corresponding to a plurality of first rounds when the SHA-1 hash calculation is performed and generates a plurality of second message data corresponding to a plurality of second rounds when the SHA-256 hash calculation is performed by using one memory, one first register, one XOR calculator, and one OR calculator, calculates a message digest by the SHA-1 hash calculation by using the plurality of first message data when the SHA-1 hash calculation is performed, and calculates a message digest by the SHA-256 by using the plurality of second message data when the SHA-256 hash calculation is performed.