.\" This file is in the public domain.
.Dd July 22, 2000
.Dt LIBDES 3
.Os NetBSD 1.4T
.Sh NAME
.Nm des ,
.Nm des3 ,
.Nm rsadestable ,
.Nm rsades3table
.Nd DES encryption routines
.Sh SYNOPSIS
.Fd #include <des.h>
.br
.Nm cc
.Op Ar arguments
.Fl ldes
.br
.Ft void
.Fn des "void *out" "const void *in" "const void *key" "int op"
.Ft void
.Fn des3 "void *out" "const void *in" "const void *key" "int op"
.Ft void
.Fn rsadestable "void *table" "const void *key"
.Ft void
.Fn rsades3table "void *table" "const void *key"
.Sh DESCRIPTION
These functions perform DES encryption.  DES is the Data Encryption
Standard, as found in USA Government Federal Information Processing
Standards Publication 46, of January 15, 1977.
.Pp
.Fn des
is the principal routine of the library.  It takes a data block in the
.Fa in
argument (which must point to eight bytes of data) and a key in the
.Fa key
argument (which must also point to eight bytes of data), encrypting or
decrypting according as the
.Fa op
argument is
.Dv ENCRYPT
or
.Dv DECRYPT .
Note that DES has only 56 bits of key; the low-order bit of each byte
in the
.Fa key
data is ignored.  The resulting output data block is stored through
.Fa out ,
which again must point to eight bytes of data.  The
.Fa in
and
.Fa out
arguments may point to identical or otherwise overlapping data areas
without harm.
.Pp
.Fn des3
performs three-key triple-DES E-D-E encryption (and decryption).  Its
interface is just like
.Fn des Ns 's,
except that
.Fa key
must point to 24, not 8, bytes of key data (again, the low bit of each
byte is ignored).  (The block size is still eight bytes.)
.Pp
.Fn rsadestable
and
.Fn rsades3table
are present for compatability with RSADSI's DES code; they compute key
table blocks believed to be identical with those computed by the RSADSI
routines
.Fn deskey
and
.Fn tripledes3key .
They exist because at least one network protocol is known to depend on
this exact key table layout.
.Sh ERRORS
These routines cannot fail unless they are passed invalid arguments.
.Sh BUGS
Ignoring the low bits of the key bytes is weird, outrageous, and
arguably stupid, but it's how almost all other DES implementations
work, and the specification does contain language implying that
something of the sort should be done.
.Pp
Only ECB mode is directly supported.  Wrapper routines should be
provided for other operating modes, CBC at the very least.
.Pp
Very slow, even among software DES implementations.
.Sh AUTHOR
der Mouse,
.Aq mouse@rodents.montreal.qc.ca .