crypt16(3) [ultrix man page]
crypt(3) Library Functions Manual crypt(3) Name crypt, crypt16, setkey, encrypt - DES encryption Syntax char *crypt(key, salt) char *key, *salt; char *crypt16(key, salt) char *key, *salt; void setkey(key) char *key; Description The subroutine is the password encryption routine. It is based on the NBS Data Encryption Standard, with variations intended to frustrate use of hardware implementations of the DES for key search. The first argument to is normally a user's typed password. The second is a 2-character string chosen from the set [a-zA-Z0-9./]. The salt string is used to perturb the DES algorithm in one of 4096 different ways, after which the password is used as the key to encrypt repeat- edly a constant string. The returned value points to the encrypted password, in the same alphabet as the salt. The first two characters are the salt itself. The subroutine is identical to the function except that it will accept a password up to sixteen characters in length. It generates a longer encrypted password for use with enhanced security features. The other entries provide primitive access to the actual DES algorithm. The argument of 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, lead- ing to a 56-bit key which is set into the machine. The argument to the entry is likewise a character array of length 64 containing 0s and 1s. The argument array is modified in place to a similar array representing the bits of the argument after having been subjected to the DES algorithm using the key set by If edflag is 0, the argument is encrypted; if non-zero, it is decrypted. Restrictions The return values from and point to static data areas whose content is overwritten by each call. Environment Default Environment In the default environment on systems that do not have the optional encryption software installed the function expects exactly one argu- ment, the data to be encrypted. The edflag argument is not supplied and there is no way to decrypt data. If the optional encryption soft- ware is installed the function behaves as it does in the POSIX environment. The syntax for the default environment follows: void encrypt(block) char *block; POSIX Environment In the POSIX environment the encrypt function always expects two arguments. The function will set errno to ENOSYS and return if edflag is non-zero and the optional encryption software is not present. The syntax for the POSIX environment follows: void encrypt(block, edflag) char *block; int edflag; In all cases the function will set errno to ENOSYS and return if the optional encryption software is not present. See Also login(1), passwd(1), yppasswd(1yp), getpass(3), auth(5), passwd(5), passwd(5yp) ULTRIX Security Guide for Users and Programmers crypt(3)
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CRYPT(3) BSD Library Functions Manual CRYPT(3) NAME
crypt, encrypt, setkey -- DES encryption SYNOPSIS
#include <unistd.h> char * crypt(const char *key, const char *salt); void encrypt(char *block, int edflag); #include <stdlib.h> void setkey(const char *key); DESCRIPTION
The crypt() function performs password encryption, based on the NBS Data Encryption Standard (DES). Additional code has been added to deter key search attempts. The first argument to crypt() is a null-terminated string, typically a user's typed password. The second is in one of two forms: if it begins with an underscore (``_''), an extended format is used in interpreting both the key and the salt value, as outlined below. Extended crypt: The key is divided into groups of 8 characters (the last group is null-padded) and the low-order 7 bits of each each character (56 bits per group) are used to form the DES key as follows: the first group of 56 bits becomes the initial DES key. For each additional group, the XOR of the encryption of the current DES key with itself and the group bits becomes the next DES key. The salt is a 9-character array consisting of an underscore, followed by 4 bytes of iteration count and 4 bytes of salt. These are encoded as printable characters, 6 bits per character, least significant character first. The values 0 to 63 are encoded as ``./0-9A-Za-z''. This allows 24 bits for both count and salt. Traditional crypt: The first 8 bytes of the key are null-padded, and the low-order 7 bits of each character is used to form the 56-bit DES key. The salt is a 2-character array of the ASCII-encoded salt. Thus, only 12 bits of salt are used. count is set to 25. Algorithm: The salt introduces disorder in the DES algorithm in one of 16777216 or 4096 possible ways (ie. with 24 or 12 bits: if bit i of the salt is set, then bits i and i+24 are swapped in the DES E-box output). The DES key is used to encrypt a 64-bit constant, using count iterations of DES. The value returned is a null-terminated string, 20 or 13 bytes (plus null) in length, consisting of the salt, followed by the encoded 64-bit encryption. The functions, encrypt() and setkey() provide access to the DES algorithm itself. setkey() is passed a 64-byte array of binary values (numeric 0 or 1). A 56-bit key is extracted from this array by dividing the array into groups of 8 and ignoring the last bit in each group. That bit is reserved for a byte parity check by DES, but is ignored by these functions. The block argument to encrypt() is also a 64-byte array of binary values. If the value of edflag is 0, block is encrypted; otherwise, it is decrypted. The result is returned in the original array block, after using the key specified by setkey() to process it. The function crypt() returns a pointer to the encrypted value on success, and NULL on failure. The crypt() and setkey() functions all manipulate the same key space. SEE ALSO
login(1), passwd(1), getpass(3), compat(5), passwd(5) LEGACY SYNOPSIS
#include <unistd.h> int encrypt(char *block, int edflag); The function encrypt() returns 0 on success and 1 on failure. void setkey(const char *key); The include file <unistd.h> is necessary and sufficient for the setkey() function. BUGS
The crypt() function returns a pointer to static data, and subsequent calls to crypt() will modify the same object. HISTORY
A rotor-based crypt() function appeared in Version 6 AT&T UNIX. The current style crypt() first appeared in Version 7 AT&T UNIX. This library (FreeSec 1.0) was developed outside the United States of America as an unencumbered replacement for the U.S.-only libcrypt encryption library. Programs linked against the crypt() interface may be exported from the U.S.A. only if they use crypt() solely for authentication purposes and avoid use of the other programmer interfaces listed above. Special care has been taken in the library so that programs which only use the crypt() interface do not pull in the other components. AUTHOR
David Burren <davidb@werj.com.au> FreeSec 1.0 March 9, 1994 FreeSec 1.0