MD5 Homepage (unofficial)

MD5: Introduction

MD5 was developed by Professor Ronald L. Rivest of MIT. What it does, to quote the executive summary of rfc1321, is:

[The MD5 algorithm] takes as input a message of arbitrary length and produces as output a 128-bit "fingerprint" or "message digest" of the input. It is conjectured that it is computationally infeasible to produce two messages having the same message digest, or to produce any message having a given prespecified target message digest. The MD5 algorithm is intended for digital signature applications, where a large file must be "compressed" in a secure manner before being encrypted with a private (secret) key under a public-key cryptosystem such as RSA.

In essence, MD5 was a way to verify data integrity, and is much more reliable than checksum and many other commonly used methods. However, it is now obsolete, and should no longer be used for new implementations.

Is MD5 perfect? A cryptographic algorithm is rarely provably perfect. Cryptographers examine and test algorithms as carefully as possible, but few stand the test of time. MD5 has known problems. See below for more information.

NEWS:

As of 2008-12-30, MD5's use in PKI is now problematic. Because of the collision weakness noted below, two certificate signing requests can be generated with the same hash, one for a legitimate destination, one for a victim or wildcard destination. The legit request is sent to a certificate authority that still uses MD5. The CA signs the legitimate request. The requestor can then use that signature for the victim/wildcard certificate.

As of 2004, MD5 has a known collision weakness. See the technical article about the collisions, read more meta-info about the collisions, and read an FAQ on the impact of the MD5 collisions. Synopsis: MD5 is not completely useless, but is now problematic for certain uses.

Implementations

Apple IIgs

MD5 for the Apple IIgs. Link provided by Andrew Roughan.

ASP

MD5 in ASP. Written by Thomas Nielsen; hosted per his request.
MD5 in ASP 2.0. Reference by Andrea Giammarchi.

C

Professor Rivest's original implementation is included in the appendix of rfc1321 and is also available in a more easily extracted (tarred, gzipped) form.
L. Peter Deutsch's implementation, with a different license that he calls BSD-like: MD5 in C. The author says: "This implementation was written directly from the text of RFC 1321 (exclusive of the Appendices), does not incorporate any part of the RSA documentation or software, and therefore does not require any acknowledgement to RSA."
Colin Plumb, Branko Lankester, Ian Jackson, and Galen Hazelwood's md5sum: md5sum. Note that this package appears to assume that you use Debian Linux.
Christophe Devine's MD5. Reference by author.

C++

Is available here in tarred, gzipped form. Version 1.02.

C#/.Net

Apparently, MD5 is a built-in for .net/C#. Thanks, Richard Maw, for letting me know.

Coldfusion

Coldfusion includes MD5 natively per Steve R. Seaquist.

command-line

Another md5sum. Reference by Tom Lynn.

Delphi

Sarah Dean includes MD5 support in a collection of Delphi components.

Java

Jari Juslin reports that as of version 1.4.0, Java supports MD5 natively. You can read more about it at Sun's documentation of MD5 for java.
MD5 for Java. Reference by benjamin pritchard.

Javascript

Paul Johnston has created a javascript MD5 implementation of MD5 under the BSD license.
MD5 for Javascript. Reference by Dominik Deobald.

Lua

MD5 for Lua, by Roberto Ierusalimschy. Reference by author.

Lotus Script

MD5 in Lotus Script, by Martin Wendt. Reference by author.

Macromedia Director

MD5 for Macromedia Director by Chuck Neal. Reference by Chuck Neal.

masm32

MD5 in ASM. Reference by "Mike"/MB.

Miva

Petr Kutil and Ivo Truxa have created a Mivo implementation of MD5.

MySQL

Apparently, MD5 is a builtin for MySQL. More power to them! Thanks to Jared Kuolt for the reference.

Perl5

MD5 support is now built-in to recent perls, and called Digest::MD5.
Neil Winton has created an MD5 Perl Module. This is a Perl Extension, requiring additional compilation.

PHP

Looks like MD5 is a builtin for PHP. More power to them!
An MD5 file parser class for PHP. Reference from Kirill Zinov.

PostgreSQL

Looks like MD5 is a builtin for PostgreSQL. More power to them! (Reference provided by Ben Wahlstrand.)

Python

Several people have written in to say that MD5 is a builtin for Python. More power to them!

REBOL

Rebol has built-in support for MD5 per Gregg Irwin.

REXX

MD5 in REXX for OS/2. Reference by Frank Ellermann.
Another MD5 in REXX. Reference by Frank Ellermann.

Scheme

MD5 for Scheme. (reference by Jens Axel Søgaard, the author)

SQL Server

For SQL Server 7/2000 by Joseph Gama, reference by author. NOTE: link appears to be down. Send me email if you want a copy.
For SQL Server 2000, by Vic Mackey, reference by Mark Kincaid.

TCL

tcllib includes MD5 support as per the tcllib MD5 docs. (reference by Andrew Ho.)

Visual Basic

Francisco Carlos Piragibe de Almeida has created a DLL with a BAS wrapper module for use in VB projects (19K download)
and an ActiveX in-process server wrapper around the original DLL (includes the DLL) (1394K download). (appears to be broken -- 2005-11-14)
MD5 for VB. Reference by benjamin pritchard.
MD5 for VB and VBScript. Reference by Dominik Deobald.

Windows

Note: assorted language implementations also apply.
MD5 command-line for Windows. Reference by Stacy Curl.
Irnis apparently produces a commercial GUI for MD5 and other hash algorithms. Reference by Irnis I.Haliullin.
Fastsum. Reference by Kirill Zinov, the author.
MD5Check; includes 32-bit and 64-bit implementations. Free for non-commercial use. Reference by Mark Gillespie, the author.

Witango

Apparently, the Witango product supports MD5 per Jennifer M. Humphreys.

Collision generators

Patrick Stach wrote an MD5 collision generator and an MD4 collision generator.

RSA's MD5 disclaimer

License to copy and use this software is granted provided that it is identified as the "RSA Data Security, Inc. MD5 Message-Digest Algorithm" in all material mentioning or referencing this software or this function.

License is also granted to make and use derivative works provided that such works are identified as "derived from the RSA Data Security, Inc. MD5 Message-Digest Algorithm" in all material mentioning or referencing the derived work.

RSA Data Security, Inc. makes no representations concerning either the merchantability of this software or the suitability of this software for any particular purpose. It is provided "as is" without express or implied warranty of any kind.

These notices must be retained in any copies of any part of this documentation and/or software.

This page maintained by Mordechai T. Abzug. If you want to add a link, send mail to mabzug1@umbc.edu.