Hash Coding calculate a number, called a hash Hash coding is a process that uses a hash algorithm to almost value, from a message of any length. It is a fingerprint for the message because it is certain to be unique for each message. Good hash algorithms are designed so that the probability of two different messages resulting in the same hash value, which would create a collision, is extremely small. Hash coding is a particularly convenient way to tell hash whether a message has been altered in transit because its original hash value and the value computed by the receiver will not match after a message is altered.