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Alphabetical listing for C

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crypt(3)
NAME
  crypt, crypt16, setkey, encrypt - DES encryption

SYNOPSIS
  #include <unistd.h>
  #include <stdlib.h>

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

  char *crypt16(
	  const char *key,
	  const char *salt );

  void setkey(
	  const char *key );

DESCRIPTION
  The crypt() 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 crypt() 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 repeatedly 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 crypt16() subroutine is identical to the crypt() 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 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, leading to a 56-
  bit key which is set into the machine.

  The argument to the encrypt() 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 setkey(). If edflag is
  0, the argument is encrypted; if non-zero, it is decrypted.

RESTRICTIONS
  The return values from crypt() and crypt16() 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 encrypt() function expects exactly one
  argument, the data to be encrypted. The edflag argument is not supplied and
  there is no way to decrypt data. If the optional encryption software is
  installed the encrypt() 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 encrypt() 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 setkey() function will set errno to ENOSYS and return if
  the optional encryption software is not present.

SEE ALSO
  login(1), passwd(1), yppasswd(1), getpass(3), passwd(4), prpasswd(4)

Index for Section 3

Alphabetical listing for C

Top of page