CRYPT(3X)            INTERACTIVE UNIX System            CRYPT(3X)



          NAME
               crypt - password and file encryption functions

          SYNOPSIS
               cc [flag ...] file ... -lcrypt [library ...]

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

               void setkey (key)
               char *key;

               void encrypt (block, flag)
               char *block;
               int flag;

               char *des_crypt (key, salt)
               char *key, *salt;

               void des_setkey (key)
               char *key;

               void des_encrypt (block, flag)
               char *block;
               int flag;

               int run_setkey (p, key)
               int p[2];
               char *key;

               int run_crypt (offset, buffer, count, p)
               long offset;
               char *buffer;
               unsigned int count;
               int p[2];

               int crypt_close(p)
               int p[2];

          DESCRIPTION
               des_crypt 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 dif-
               ferent 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.



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               The des_setkey and des_encrypt entries provide (rather prim-
               itive) access to the actual hashing algorithm.  The argument
               of des_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; this gives a 56-bit key which is set
               into the machine.  This is the key that will be used with
               the hashing algorithm to encrypt the string block with the
               function des_encrypt.

               The argument to the des_encrypt 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 des_setkey.  If edflag is zero, the argument is
               encrypted; if non-zero, it is decrypted.

               Note that decryption is not provided in the international
               version of crypt(3X).  The international version is part of
               the C Programming Language Utilities, and the domestic ver-
               sion is part of the Security Administration Utilities.  If
               decryption is attempted with the international version of
               des_encrypt, 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 run_setkey and run_crypt 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.  Run_setkey establishes a two-
               way pipe connection with crypt(1), using key as the password
               argument.  Run_crypt takes a block of characters and
               transforms the cleartext or ciphertext using crypt(1).
               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 con-
               nection is an array containing indices to a table of input
               and output file streams.  When encryption is finished,
               crypt_close is used to terminate the connection with
               crypt(1).

               Run_setkey returns -1 if a connection with crypt(1) cannot
               be established.  This will occur on international versions
               of the UNIX system where crypt(1) is not available.  If a
               null key is passed to run_setkey, 0 is returned.  Otherwise,
               1 is returned.  Run_crypt returns -1 if it cannot write out-
               put or read input from the pipe attached to crypt.  Other-
               wise it returns 0.

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


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          CRYPT(3X)            INTERACTIVE UNIX System            CRYPT(3X)



               crypt(1), login(1), passwd(1) in the INTERACTIVE UNIX System
               User's/System Administrator's Reference Manual.

          DIAGNOSTICS
               In the international version of crypt(3X), a flag argument
               of 1 to des_encrypt is not accepted, and an error message is
               printed.

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












































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