Close the digest, producing the final digest value and resetting the digest.
* close the digest, producing the final digest value. The doFinal * call leaves the digest reset.
update the message digest with a block of bytes.
reset the digest back to it's initial state.
Used for padding (i.e. in HMacs)
return the size, in bytes, of the digest produced by this message digest.
create an independant copy of this Digest and it's full state