NAME
crypt, setkey, encrypt — generate hashing encryption
SYNOPSIS
#include <crypt.h>
#include <unistd.h>
char *crypt(const char *key, const char *salt);
void setkey(const char *key);
void encrypt(char block[64], int edflag);
Obsolescent Interfaces
char *crypt_r(const char *key, const char *salt, CRYPTD *cd);
void setkey_r(const char *key, CRYPTD *cd);
void encrypt_r(char block[64], int edflag, CRYPTD *cd);
DESCRIPTION
crypt():
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.
setkey() and encrypt():
setkey()
and
encrypt()
provide (rather primitive) access to the actual hashing algorithm.
The argument to
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 is used with the hashing algorithm
to encrypt or decrypt the string
block
with the function
encrypt().
The
block
argument to
encrypt()
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 that was set by
setkey().
If
edflag
is zero, the argument is encrypted; if non-zero it is decrypted.
Obsolescent Interfaces
crypt_r(),
setkey_r(),
encrypt_r()
generate hashing encryption.
APPLICATION USAGE
crypt(),
encrypt()
and
setkey()
are thread-safe. These interfaces are not async-cancel-safe.
WARNINGS
The return value for
crypt()
points to data whose content is overwritten
by each call.
crypt_r(),
setkey_r(),
and
encrypt_r()
are obsolescent interfaces supported only for compatibility with
existing DCE applications. New multithreaded applications should
use
crypt(),
encrypt()
and
setkey().
STANDARDS CONFORMANCE
crypt(): SVID2, SVID3, XPG2, XPG3, XPG4
encrypt(): SVID2, SVID3, XPG2, XPG3, XPG4
setkey(): SVID2, SVID3, XPG2, XPG3, XPG4
