Description:

The *sha256* module allows you to use the NIST SHA 256/384/512 hash
algorithm.

A new sha256 context object is created with the *new* operation followed by
a digest size which may be either 256, 384, or 512 bits. Multiple
simultaneous digest context can be maintained if desired. The context is
updated with the *add* operation which adds the strings contained in the
_LIST_ parameter.

The final message digest value is returned by the *digest* operation as a
32-, 48-, or 64-byte binary string. This operation delivers the result of
operations since the last *new* or *reset* operation. Once the operation
has been performed, the context must be *reset* before being used to
calculate another digest value.