This document discusses the Message Digest 5 (MD5) hashing algorithm. It provides an overview of MD5, including how it works to generate hashes and check integrity. However, the document notes that MD5 is no longer considered secure due to flaws that allow hash collisions to be generated with relative ease. More robust hashing algorithms like SHA or Whirlpool are now recommended instead of MD5.

1. Message Digest5
Prof. Neeraj Bhargava
Kapil Chauhan
Department of Computer Science
School of Engineering & Systems Sciences
MDS University, Ajmer

2. Introduction
Initial checking of integrity – checksums, then CRC
These are only good at detecting lost information due
to hardware or transmission errors

3. Potential Attack
A wants to obtain privileges from B
A generates two messages with the same hash
values
A presents an innocent message to B for his
digital signature
A applies the signature to the other malicious
message with the same hash

4. MD5
The solution lay in one-way hashing algorithms
These should keep two messages from colliding
They should also be sufficiently difficult to
reverse-engineer

5. MD5
MD5 represents the fifth iteration designed by
Ronald Rivest (RSA)
Others from other authors include Whirlpool and
SHA
MD5 is open-source and released under the GPL
MD5 is optimized for use on 32-bit computers

6. MD5 Hashing
MD5("The quick brown fox jumps over the lazy dog") =
9e107d9d372bb6826bd81d3542a419d6
MD5("The quick brown fox jumps over the lazy cog") =
1055d3e698d289f2af8663725127bd4b
MD5("") = d41d8cd98f00b204e9800998ecf8427e

7. Modern Flaws
MD5 uses a short 128-bit hash
MD5 has become a popular hashing tool through
PHP
PASSWORD HASHING
Rivest says his algorithm was never designed for
this usage
Long messages that need an integrity check
before encryption

8. MD5 Flaws
Rainbow tables for passwords
COLLISIONS!

9. MD5 Collisions
2004 Wang et. al delivered an algorithm that could
produce collisions in a few hours on an IBM p690
cluster
Algorithm was improved by Lenstra et. al in 2005 to a
few hours on a single laptop

10. Conclusion
A digest algorithm does not provide integrity if
collisions are so simple to produce
SHA or Whirlpool should be considered until a
replacement for MD5 can be found