---
name: "MD5Transform"
section: "9"
platform: "linux"
package: "freebsd-manpages"
version: "6.0-5"
release: "Debian 4.0 (Etch)"
platforms: ["linux"]
url: "https://new.carta.tech/MD5Transform/9"
---

# MD5Transform(9)

message digest routines

## NAME

**MD5**, **MD5Init**, **MD5Transform** – message digest routines

## SYNOPSIS

**#include \<sys/types.h\>**

**#include \<sys/md5.h\>**

*void*\

**MD5Init**(*MD5\_CTX \*buf*);

*void*\

**MD5Transform**(*u\_int32\_t buf\[4\]*, *const unsigned char block\[64\]*);

## DESCRIPTION

The **MD5** module implements the RSA Data Security, Inc. MD5 Message-Digest Algorithm (MD5). It produces 128-bit MD5 Digest of data.

- *MD5Init*

  must be called just before **MD5Transform**() will be used to produce a digest. The *buf* argument is the storage for the digest being produced on subsequent calls to the **MD5Transform**() routine.

- *MD5Transform*

  is the core of the MD5 algorithm, this alters an existing MD5 hash kept in *buf* to reflect the addition of 64 characters of new data passed in *block* argument.

## COPYRIGHTS

The code for MD5 transform was taken from Colin Plumb's implementation, which has been placed in the public domain. The MD5 cryptographic checksum was devised by Ronald Rivest, and is documented in RFC 1321, "The MD5 Message Digest Algorithm".