crypt(3X)             UNIX System V(Encryption Utilities)             crypt(3X)


NAME
      crypt - 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 *descrypt (const char *key, const char *salt);

      void dessetkey (const char *key);

      void desencrypt (char *block, int flag);

      int runsetkey (int *connection, const char *key);

      int runcrypt (long offset, char *buffer, unsigned int count,
          int *connection);

      int cryptclose(int *connection);

DESCRIPTION
      descrypt 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 dessetkey and desencrypt entries provide (rather primitive) access
      to the actual hashing algorithm.  The argument of dessetkey 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
      desencrypt.

      The argument to the desencrypt 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


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crypt(3X)             UNIX System V(Encryption Utilities)             crypt(3X)


      using the key set by dessetkey.  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 Encryption Utilities.  If decryption
      is attempted with the international version of desencrypt, 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 runsetkey and runcrypt 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.
      runsetkey establishes a two-way pipe connection with the crypt utility,
      using key as the password argument.  runcrypt 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 buffer is coming from.  count is the number of characters in
      buffer, and connection is an array containing indices to a table of input
      and output file streams.  When encryption is finished, cryptclose is
      used to terminate the connection with the crypt utility.

      runsetkey 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 runsetkey, 0 is returned.  Otherwise, 1 is returned.
      runcrypt 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.

SEE ALSO
      getpass(3C), passwd(4)
      crypt(1), login(1), passwd(1) in the User's Reference Manual

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

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







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