Merkle-Damgard constructions is absolutely different from every other crypto Software. In Cryptography Merkle-Damgard constructions or Merkle-Damgard hash Function is a method of building collision-resistant cryptographic hash functions from collision one-way compression functions. This construction is used in the design of many popular Hash algorithms such as MD5, SHA-1 and SHA-256 designed by the united States National Security Agency first Published in 2001, Using the Davies-Meyer Structure from a specialised block cipher.