.\" FreeSec: libcrypt for NetBSD
.\"
.\" Copyright (c) 1994 David Burren
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.\" $FreeBSD: src/secure/lib/libcipher/cipher.3,v 1.6.2.3 2001/12/14 15:21:13 ru Exp $
.\" $DragonFly: src/secure/lib/libcipher/cipher.3,v 1.2 2003/06/17 04:27:48 dillon Exp $
.\"
.\" Manual page, using -mandoc macros
.\"
.Dd March 9, 1994
.Dt CIPHER 3
.Os
.Sh NAME
.Nm setkey ,
.Nm encrypt ,
.Nm des_setkey ,
.Nm des_cipher
.Nd DES encryption
.Sh LIBRARY
.Lb libcipher
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn setkey "const char *key"
.Ft int
.Fn encrypt "char *block" "int flag"
.Ft int
.Fn des_setkey "const char *key"
.Ft int
.Fn des_cipher "const char *in" "char *out" "long salt" "int count"
.Sh DESCRIPTION
The functions,
.Fn encrypt ,
.Fn setkey ,
.Fn des_setkey
and
.Fn des_cipher
provide access to the
.Tn DES
algorithm.
.Fn setkey
is passed a 64-byte array of binary values (numeric 0 or 1).
A 56-bit key is extracted from this array by dividing the
array into groups of 8, and ignoring the last bit in each group.
That bit is reserved for a byte parity check by DES, but is ignored
by these functions.
.Pp
The
.Fa block
argument to
.Fn encrypt
is also a 64-byte array of binary values.
If the value of
.Fa flag
is 0,
.Fa block
is encrypted otherwise it is decrypted.
The result is returned in the original array
.Fa block
after using the key specified by
.Fn setkey
to process it.
.Pp
The argument to
.Fn des_setkey
is a character array of length 8.
The least significant bit (the parity bit) in each character is ignored,
and the remaining bits are concatenated to form a 56-bit key.
The function
.Fn des_cipher
encrypts (or decrypts if
.Fa count
is negative) the 64-bits stored in the 8 characters at
.Fa in
using
.Xr abs 3
of
.Fa count
iterations of
.Tn DES
and stores the 64-bit result in the 8 characters at
.Fa out
(which may be the same as
.Fa in ) .
The
.Fa salt
introduces disorder in the
.Tn DES
algorithm in one of 16777216 or 4096 possible ways
(ie. with 24 or 12 bits: if bit
.Em i
of the
.Ar salt
is set, then bits
.Em i
and
.Em i+24
are swapped in the
.Tn DES
E-box output).
.Pp
The functions
.Fn setkey ,
.Fn encrypt ,
.Fn des_setkey ,
and
.Fn des_cipher
return 0 on success and 1 on failure.
.Pp
The
.Fn setkey
and
.Fn des_setkey
functions manipulate the same key space.
.Sh SEE ALSO
.Xr login 1 ,
.Xr passwd 1 ,
.Xr crypt 3 ,
.Xr getpass 3 ,
.Xr passwd 5
.Sh HISTORY
This library (FreeSec 1.0) was developed outside the United States of America
as an unencumbered replacement for the U.S.-only
.Nx
libcrypt encryption
library.
Users should be aware that this code (and programs staticly linked with it)
may not be exported from the U.S., although it apparently can be imported.
.Sh AUTHORS
.An David Burren Aq davidb@werj.com.au