What is Merkle Damgard scheme?

In cryptography, the Merkle–Damgård construction or Merkle–Damgård hash function is a method of building collision-resistant cryptographic hash functions from collision-resistant one-way compression functions. This construction was used in the design of many popular hash algorithms such as MD5, SHA-1 and SHA-2.

How does Merkle Damgard work?

The idea of the Merkle-Damgård construction is to split the input x into blocks of size t. The end of the string is filled out with 0s if necessary. A final block called the “padding block” is added, which encodes the (original) length of x in binary.

How do you create a hash function?

With modular hashing, the hash function is simply h(k) = k mod m for some m (usually, the number of buckets). The value k is an integer hash code generated from the key. If m is a power of two (i.e., m=2p), then h(k) is just the p lowest-order bits of k.

What is collision-resistant hash function?

In cryptography, collision resistance is a property of cryptographic hash functions: a hash function H is collision-resistant if it is hard to find two inputs that hash to the same output; that is, two inputs a and b where a ≠ b but H(a) = H(b). Those functions are called provably secure.

What kind of construction is Merkle Damgard hash function?

In this section, we’ll see one approach for constructing hash functions, called the Merkle-Damgård construction. Instead of a full-fledged hash function, imagine that we had a collision-resistant function (family) whose inputs were of a single fixed length, but longer than its outputs.

When did Ralph Merkle and Ivan Damgard create the Merkle – Damgard construction?

The Merkle–Damgård construction was described in Ralph Merkle’s Ph.D. thesis in 1979. Ralph Merkle and Ivan Damgård independently proved that the structure is sound: that is, if an appropriate padding scheme is used and the compression function is collision-resistant, then the hash function will also be collision-resistant.

How is length padding used in Merkle Damgard construction?

This is called length padding or Merkle–Damgård strengthening . In the diagram, the one-way compression function is denoted by f, and transforms two fixed length inputs to an output of the same size as one of the inputs. The algorithm starts with an initial value, the initialization vector (IV).