Hash chain

A hash chain is the successive application of a cryptographic hash function to a piece of data. In computer security, a hash chain is a method to produce many one-time keys from a single key or password. For non-repudiation a hash function can be applied successively to additional pieces of data in order to record the chronology of data's existence.

A hash chain is a successive application of a cryptographic hash function ${\displaystyle h}$ to a string ${\displaystyle x}$.

For example,

${\displaystyle h(h(h(h(x))))}$ gives a hash chain of length 4, often denoted ${\displaystyle h^{4}(x)}$

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