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# ChainHash Definitions

chain variable
  a variable taking value in the set of all bit strings of a specified length.
block
  a bit string of a specified length.
compression function
  a function from the product space of the domains of a specified set of chain variables and the set of all blocks of a specified length to the product space of the domains of the chain variables.
initial value
  an explicitly specified point in the product space of the domains of a set of chain variables.
padding algorithm
  an algorithm which appends bits to a bit string giving a new bit string whose length has some desired propery.
chain hash function
  a function constructed from a compression function, padding algorithm, and an initial value in such a manner as to have the following properties:
  - Its domain is either all bits string up to some specified length, or arbitrary length bit strings.
  - Its range is equal to the range of the compression function.
  - The value of the function at a bit string is determined as follows:
    - The bit string is padded by using the padding algorithm to increase its length to a multiple of the size of the blocks of the compression function.
    - The chain variables are set equal to the initial value.
    - For each block in the padded message, the chain variables' values are updated to the value of the compression function at the point specified by the chain variable and the block.
    - The value of the chain hash function is equal to the concatenation of the final values of the chain variables.

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