DES(3)                 C LIBRARY FUNCTIONS                 DES(3)



NAME
     desinit, setkey, endes, dedes, desdone - DES encryption

SYNOPSIS
     desinit(mode) int mode;

     setkey(key) char *key;

     endes(block) char *block;

     dedes(block) char *block;

     desdone();

DESCRIPTION
     These routines implement both standard and modified forms of
     the  NBS Data Encryption Standard (DES). The user must first
     call desinit with one of three operating modes:

     0 - Standard, vanilla DES.

     1 - DES with the initial and final permutations removed.  As
     these permutations do not strengthen the algorithm, they are
     widely regarded as having no purpose other than to slow down
     software implementations.  Removing them speeds it up but of
     course the algorithm is no longer standard and it  will  not
     be compatible with hardware DES chips.

     2 - DES with the initial and final permutations removed, and
     with  independent  48-bit subkeys for each of the 16 rounds.
     Needless to say this is even less standard than mode 1,  but
     if properly used (randomize ALL key bytes -- no padding!) it
     should strengthen the algorithm.

     After calling desinit the user next calls setkey. In modes 0
     and  1,  8 key bytes are expected, with the low order bit of
     each key byte ignored (parity is not checked). This gives  a
     56-bit key.  In mode 2, 128 key bytes are expected; the high
     order 2 bits of each byte are ignored, giving a 768 bit key.
     In  this  mode,  the first 8 bytes will be used in the first
     round, the second 8 bytes in the second round, and so on.

     Once the key is set, the user may perform  in-place  encryp-
     tion  and  decryption of 8-byte blocks of data with calls to
     endes and dedes.

     To free up memory dynamically allocated by desinit the  user
     may  call desdone. If further encryption or decryption is to
     be done, desinit and setkey must be called again.

AUTHOR
     Phil Karn, KA9Q, building  heavily  on  the  earlier  public



Sun Release 3.4    Last change: 24 March 1987                   1






DES(3)                 C LIBRARY FUNCTIONS                 DES(3)



     domain code by Jim Gillogly.






















































Sun Release 3.4    Last change: 24 March 1987                   2