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CRYPT(3X)							     CRYPT(3X)

NAME    [Toc]    [Back]

     crypt - password and file encryption functions

SYNOPSIS    [Toc]    [Back]

     cc	[flag ...] file	... -lcrypt

     char *crypt(char *key, char *salt);

     void setkey(char *key);

     void encrypt(char *block, int flag);

     char *des_crypt(char *key,	char *salt);

     void des_setkey(char *key);

     void des_encrypt(char *block, int flag);

     int run_setkey(int	p[2], char *key);

     int run_crypt(long	offset,	char *buffer, unsigned int count, int p[2]);

     int crypt_close(int p[2]);

DESCRIPTION    [Toc]    [Back]

     des_crypt is the password encryption function.  It	is based on a one way
     hashing encryption	algorithm with variations intended (among other
     things) to	frustrate use of hardware implementations of a key search.

     Key is a user's typed password.  Salt is a	two-character string chosen
     from the set [a-zA-Z0-9./]; this string is	used to	perturb	the hashing
     algorithm in one of 4096 different	ways, after which the password is used
     as	the key	to encrypt repeatedly a	constant string.  The returned value
     points to the encrypted password.	The first two characters are the salt

     The des_setkey and	des_encrypt entries provide (rather primitive) access
     to	the actual hashing algorithm.  The argument of des_setkey is a
     character array of	length 64 containing only the characters with
     numerical value 0 and 1.  If this string is divided into groups of	8, the
     low-order bit in each group is ignored; this gives	a 56-bit key which is
     set into the machine.  This is the	key that will be used with the hashing
     algorithm to encrypt the string block with	the function des_encrypt.

     The argument to the des_encrypt entry is a	character array	of length 64
     containing	only the characters with numerical value 0 and 1.  The
     argument array is modified	in place to a similar array representing the
     bits of the argument after	having been subjected to the hashing algorithm
     using the key set by des_setkey.  If edflag is zero, the argument is
     encrypted;	if non-zero, it	is decrypted.

									Page 1

CRYPT(3X)							     CRYPT(3X)

     Note that decryption is not provided in the international version of
     crypt.  The international version is part of the C	Development Set, and
     the domestic version is part of the Encryption Utilities.	If decryption
     is	attempted with the international version of des_encrypt, an error
     message is	printed.

     Crypt, setkey, and	encrypt	are front-end routines that invoke des_crypt,
     des_setkey, and des_encrypt respectively.

     The routines run_setkey and run_crypt are designed	for use	by
     applications that need cryptographic capabilities [such as	ed(1) and
     vi(1)] that must be compatible with the crypt(1) user-level utility.
     Run_setkey	establishes a two-way pipe connection with crypt(1), using key
     as	the password argument.	Run_crypt takes	a block	of characters and
     transforms	the cleartext or ciphertext into their ciphertext or cleartext
     using crypt(1). Offset is the relative byte position from the beginning
     of	the file that the block	of text	provided in block is coming from.
     Count is the number of characters in block, and connection	is an array
     containing	indices	to a table of input and	output file streams. When
     encryption	is finished, crypt_close is used to terminate the connection
     with crypt(1).

     If	a null key is passed to	run_setkey, 0 is returned.  Otherwise, 1 is
     returned.	Run_crypt returns -1 if	it cannot write	output or read input
     from the pipe attached to crypt. Otherwise	it returns 0.

     The routines above	are  found in the library ``libcrypt.a'', and are
     loaded if the option ``-lcrypt'' is used with cc(1) or ld(1).

SEE ALSO    [Toc]    [Back]

     crypt(1), login(1), passwd(1), getpass(3C), passwd(4).

NOTES    [Toc]    [Back]

     In	the international version of crypt(3X),	a flag argument	of 1 to
     encrypt or	des_encrypt is not accepted, and errno is set to ENOSYS	to
     indicate that the functionality is	not available.

     The return	value in crypt points to static	data that are overwritten by
     each call.

									PPPPaaaaggggeeee 2222
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