1. Team Grey Skies – Pete Biancaniello and Anton Schraut January 18 th, 2012

2.  Designed as part of a series by Professor Ronald Rivest (MIT)  Proposed and released 1991  Used for data integrity checks  Variable-length to 128 bit output  1996, collision found in compression function  2004, In March MD5CRK started, by August an attack was complete (1 hour IBM p690 cluster)  2010, single-block collision discovered

3.  Variable input is padded to be divisible by 512.  Single bit with value 1 is appended, followed by enough zeroes to reach 64 bits less than a 512 multiple.  Last 64 bits are filled with a little endian integer representing original message length in bits.

4.  Padded input divided into 512-bit chunks  Four 32-bit words are initialized to specific constants  Each chunk is operated on in four stages called “rounds”  Each round modifies the 128-bit state composed of the initial 32-bit words

5.  Rounds consist of 16 operations  Each operation is based on one of four non- linear functions F, modular addition, and left rotation.  Possible F functions:

6.  Mi is a 32-bit block of message  Ki is a 32-bit constant  F is an “F” function  <<<s is a left rotation by s places  Each box denotes modular addition (2^32)

7.  Specifications: http://www.kleinschmidt.com/edi/md5.htm http://www.kleinschmidt.com/edi/md5.htm  Improvements/Insights: http://www.cs.colorado.edu/~jrblack/papers /md5e-full.pdf http://www.cs.colorado.edu/~jrblack/papers /md5e-full.pdf  History/General: http://en.wikipedia.org/wiki/Md5 http://en.wikipedia.org/wiki/Md5