Merkle Damgard Construction

A method of building Hash Collision resistant function. Alternative to Sponge Construction

Construction

• Message $M$ split into fixed length blocks. $M=m_0||m_1||\dots ||m_t$
• Message blocks compressed one after another using a Compression Function $f$ to produce chaining variable $h_i$ that is used to compress $m_{i+1}$
• In other words, Compression Function $f(m_i,h_{i-1})=h_i$
• $h_0$ is a fixed constant