MD5 Homepage (unofficial)
MD5 was developed by
Professor Ronald L. Rivest of MIT. What it does, to quote the executive
[The MD5 algorithm] takes as input a message of arbitrary length and
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
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,
an FAQ on the impact of the MD5 collisions. Synopsis: MD5 is not
completely useless, but is now problematic for certain uses.
- Apple IIgs
- 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
md5sum. Note that this package appears to
assume that you use Debian Linux.
Christophe Devine's MD5. Reference by author.
- Is available
here in tarred, gzipped form. Version 1.02.
- Another md5sum.
Reference by Tom Lynn.
- Lotus Script
- Macromedia Director
- MD5 support is now built-in to recent perls, and called
- Neil Winton has created an
MD5 Perl Module. This is a
Perl Extension, requiring additional compilation.
- SQL Server
- Visual Basic
- 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.
- Apparently, the Witango
product supports MD5 per Jennifer M. Humphreys.
RSA's MD5 disclaimer
Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
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.
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