Tribblix: manual page: crypt.3ext

CRYPT(3EXT) Extended Library Functions CRYPT(3EXT)

NAME

crypt, setkey, encrypt, des_crypt, des_setkey, des_encrypt,
run_setkey, run_crypt, crypt_close - password and file encryption
functions

SYNOPSIS

cc [ flag ... ] file ... -lcrypt [ library ... ]
#include <crypt.h>

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

void setkey(const char *key);

void encrypt(char *block, int flag);

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

void des_setkey(const char *key);

void des_encrypt(char *block, int flag);

int run_setkey(int *p, const char *key);

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

int crypt_close(int *p);

DESCRIPTION

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 itself.

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, thereby creating a 56-bit
key that is set into the machine. This key 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 flag is
zero, the argument is encrypted; if non-zero, it is decrypted.

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 Security Administration
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). run_setkey() establishes a two-way pipe connection with the
crypt utility, 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 the crypt utility. 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 the
crypt utility.

run_setkey() returns -1 if a connection with the crypt utility
cannot be established. This result will occur in international
versions of the UNIX system in which the crypt utility is not
available. 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 program must be linked with the object file access routine
library libcrypt.a.

RETURN VALUES

In the international version of crypt(), 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.

ATTRIBUTES

NOTES