crypt(3X)           (C Programming Language 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 *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.





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   crypt(3X)           (C Programming Language Utilities)            crypt(3X)


         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 in the international version of
         crypt.  The international version is part of the C Development Set,
         and the domestic version is part of the Security Administration
         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 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 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.

   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.

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





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   crypt(3X)           (C Programming Language Utilities)            crypt(3X)


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


















































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