DEFINITION MODULE MD5;

        (********************************************************)
        (*                                                      *)
        (*                  MD5 ENCRYPTION                      *)
        (*                                                      *)
        (*  MD5 message-digest algorithm as defined in RFC 1321 *)
        (*                                                      *)
        (*  Processes a data sequence of arbitrary length,      *)
        (*  producing a 16-byte "digest" as a secure signature  *)
        (*  of this data sequence.                              *)
        (*                                                      *)
        (*  Programmer:         P. Moylan                       *)
        (*  Started:            14 September 1998               *)
        (*  Last edited:        4 May 2021                      *)
        (*  Status:             Working                         *)
        (*                                                      *)
        (*  This module is derived from the RSA Data Security,  *)
        (*  Inc. MD5 Message-Digest Algorithm.                  *)
        (*                                                      *)
        (********************************************************)

FROM SYSTEM IMPORT CARD8, CARD32, LOC;

TYPE
    MD5_CTX;    (* is private *)
    MD5_DigestType = ARRAY [0..3] OF CARD32;


PROCEDURE MD5Init(): MD5_CTX;

    (* MD5 initialization. Begins an MD5 operation, creating a new context. *)

PROCEDURE MD5Update (context: MD5_CTX;  VAR (*IN*) data: ARRAY OF LOC;  length: CARDINAL);

    (* MD5 block update operation. Continues an MD5 message-digest operation,   *)
    (* adding more data to what has already been processed for this context.    *)

PROCEDURE MD5Final (VAR (*INOUT*) context: MD5_CTX;
                                  VAR (*OUT*) digest: ARRAY OF CARD8);

    (* MD5 finalization. Ends an MD5 message-digest operation, returning    *)
    (* 1 16-byte message digest and discarding the context.                 *)

PROCEDURE MD5DigestToString (VAR (*IN*) digest: ARRAY OF CARD8;
                             VAR (*OUT*) result: ARRAY OF CHAR);

    (* Converts the digest to a 32-character string.  If there is not enough    *)
    (* space for 32 characters, produces a leading substring of the full result.*)

END MD5.

