add_body() - feeds part of the body into the algorithm/canonicalization

  $algorithm->add_body("This is the body.\015\012");
  $algorithm->add_body("Another line of the body.\015\012");

The body should be fed one "line" at a time.

add_header() - feeds a header field into the algorithm/canonicalization

  $algorithm->add_header("Subject: this is the subject\015\012");

The header must start with the header field name and continue through any folded lines (including the embedded <CRLF> sequences). It terminates with the <CRLF> at the end of the header field.

finish_body() - signals the end of the message body

  $algorithm->finish_body

Call this method when all lines from the body have been submitted. After calling this method, use sign() or verify() to get the results from the algorithm.

finish_header() - signals the end of the header field block

  $algorithm->finish_header;

Call this method when all the headers have been submitted.

sign() - generates a signature using a private key

  $base64 = $algorithm->sign($private_key);

signature() - get/set the signature worked on by this algorithm

  my $old_signature = $algorithm->signature;
  $algorithm->signature($new_signature);

verify() - verifies a signature

  $result = $algorithm->verify();

Must be called after finish_body().

The result is a true/false value: true indicates the signature data is valid, false indicates it is invalid.

For an invalid signature, details may be obtained from $algorithm->{verification_details} or $@.