Some cryptographic hash functions implemented in Lisp

Gene Michael Stover

created Saturday, 2008 April 19
updated Saturday, 2008 April 19

1 What is this?

Pretend you didn't see this. It's under construction. Come back in a week or so, about 2008 April 26. - gene

Here are implementations in Common Lisp of three cryptographic hash functions: MD4, MD5, & SHA-1.

2 The algorithms

MD4 is defined in RFC 1320 [1].

3 Features

Stand-alone, doesn't require libraries other than Common Lisp

4 Limitations

Operates on messages whose lengths are integral multiples of eight bits. In other words, operates on sequences of whole octets.

5 Usage

6 License

7 Obtaining

8 Examples of padded messages

8.1 Empty message

If the message is empty, we add a full 448 bits of Stage 1 padding, followed by 0 as a 64-bit, little-endian number. Table refmap-empty displays this.

Table 1: map of an empty message after padding

offset	word 0 (hex)	word 1 (hex)	word 2 (hex)	word 3 (hex)
0	80000000	0	0	0
4	0	0	0	0
8	0	0	0	0
12	0	0	0	0

8.2 Length 1

If the message's length is 1 octet, we add 440 bits of Stage 1 padding, followed by 1 as a 64-bit, little-endian number. Assume the message's single octet is 1. Table 2 displays this.

Table 2: map of an empty message after padding

offset	word 0 (hex)	word 1 (hex)	word 2 (hex)	word 3 (hex)
0	01800000	0	0	0
4	0	0	0	0
8	0	0	0	0
12	1	0	0	0

A. Other File Formats

This document is available in multi-file HTML format at
http://cybertiggyr.com/gene/0h5/.
This document is available in Pointless Document Format (PDF) at
http://cybertiggyr.com/gene/0h5/0h5.pdf.

Bibliography

1: R. Rivest.
Rfc 1320: The md4 message-digest algorithm.
available online, April 1992.
ftp://ftp.rfc-editor.org/in-notes/rfc1320.txt.

Gene Michael Stover 2008-04-27