DES Implementation 1.0



This software may be freely distributed an modified without any restrictions
from the author.

Some files are based on other implementations and may contain restrictions
from the original author.

Additional restrictions due to national laws governing the use, import or
export of cryptographic software is the responsibility of the software user,
importer or exporter to follow.


This software is an implementation of the Data Encryption Standard (DES) as
described in "Federal Information Processing Standards Publication 46",
1977 January 15.

The implementation contains a general purpose DES library and user programs
for file encryption/decryption. The library is compatible with the DES
library from MIT (Massachusetts Institute of Technology) at function call
level, as described in the manual DES_CRYPT(3). There are also functions
available in this implementation that are not a part of the MIT library.

The header file "des.h" contains ANSI C function prototypes for all library
functions.

This library has only been compared against the MIT library through the
manual page due to export restrictions of the MIT library outside the US.


Changes from the MIT library:

	* Encryption methods using an initialization vector may return
	  a modified vector from the last iteration, making it possible
	  to chain calls to an encryption/decryption function into an
	  unbroken sequence.

	* Additional functions not in the MIT library are:

		des_dea		    - Identical to des_ecb_encrypt.
		des_key		    - Same as des_set_key without any parity
				      or weak-key test.
		des_ecb2_encrypt    - The Electronic Code Book mode of
				      encryption/decryption on a user
				      specified number of bytes.
		des_cfb8_encrypt    - The 8-bit Cipher FeedBack mode of
				      encryption/decryption on a user
				      specified number of bytes.
		des_ofb8_encrypt    - The 8-bit Output FeedBack mode of
				      encryption/decryption on a user
				      specified number of bytes.
		des_is_weak_key	    - Tests if the key is weak.
		des_is_semiweak_key - Tests if the key is semi-weak.
		des_no_key_schedule - Returns the number of different keys
				      in a key schedule.
		des_test_key_parity - Tests the key parity.
		des_set_key_parity  - Sets the key parity.
		des_random_cblock   - Generates a random value in a 64-bit
				      block.
		des_hex_to_cblock   - returns the value of a string with a
				      64-bit hexadecimal number in a 64-bit
				      block.
		des_print_cblock    - Prints a 64-bits block as a 64-bit
				      hexadecimal value on stdout.
		des_read_hexkey	    - Similar to des_read_password but
				      accepts only 64-bit hexadecimal
				      numbers.

User programs:

	* descrypt	- General purpose file encryption/decryption
			  program.

	* deskey	- Show the actual DES key generated from a string,
			  or returns a random key.

	* destest	- A simple test of the DES algorithm, useful when
			  modifying or optimizing the code. This program
			  does NOT verify that the implementation follows
			  the DES description.

	* desbench	- Simple benchmark program for the base DES
			  algorithm and key schedule generation.


The implementation has been tested on the following systems:

	SUN 4,			SUN OS 4.1 
	SUN 3,			SUN OS 4.1 
	VAX 11/750,		BSD 4.3
	IBM RT/PC,		AOS 4.3
	IBM RS/6000 320,	AIX 3.1
	IBM PS/2,		AIX 1.2 + TCF
	IBM 3090-150S/VF,	AIX/370 + TCF

					     _
					Stig Ostholm
					Department of Computer Engineering
					Chalmers University of Technology
					----------------------------------
					Email: ostholm@ce.chalmers.se
					Phone: +46 31 721703
					Fax:   +46 31 721561