crypt(3X)                      DG/UX R4.11MU05                     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 *p, const char *key);

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

       int cryptclose(int *p);

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 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 by default in DG/UX.  If
       decryption is attempted when it is not available, an error message is
       printed and errno is set to ENOSYS.  See the NOTES section, below.

       crypt, setkey, and encrypt are front-end routines that invoke
       descrypt, dessetkey, and desencrypt 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.
       The crypt(1) utility is not part of the DG/UX system.  See the NOTES
       section, below.  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 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, 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 will occur unless the crypt(1) command is
       supplied from the optional package described in the NOTES section,
       below.  DG/UX 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.

DIAGNOSTICS
       In the default 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.

SEE ALSO
       getpass(3C), passwd(4).
       crypt(1), login(1), passwd(1).

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

       DG/UX supports encryption but not decryption to comply with US export
       laws.  To add decryption to DG/UX, in locations that are acceptable
       to US law, you must purchase the AViiON Encryption Utilities Package,
       Model R005.  This package provides the crypt(1) command and a new
       libcrypt that supports decryption.



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