.\" $OpenBSD: blowfish.3,v 1.1 1997/02/16 20:58:16 provos Exp $
.\" Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
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.\" Manual page, using -mandoc macros
.\"
.Dd February 13, 1997
.Dt BLOWFISH 3
.Os "OpenBSD 2.0"
.Sh NAME
.Nm blf_key,
.Nm blf_enc,
.Nm blf_dec
.Nd Blowfish encryption
.Sh SYNOPSIS
.Fd #include <blf.h>
.Ft void
.Fn blf_key "blf_ctx *state" "const u_int8_t *key" "u_int16_t keylen"
.Ft void
.Fn blf_enc "blf_ctx *state" "u_int32_t *data" "u_int16_t datalen"
.Ft void
.Fn blf_dec "blf_ctx *state" "u_int32_t *data" "u_int16_t datalen"
.Sh DESCRIPTION
.Pa Blowfish
is a fast unpatented block cipher designed by Bruce Schneier.
It basically consists of a 16 times iterated Feistel network.
The block size is 64 bit and the key size is maximal 448 bit.
.Pp
The
.Fn blf_key
function initializes the 4 8bit S-boxes and the 18 Subkeys with
the hexadecimal digits of Pi. The key is used for further randomization.
The first argument to
.Fn blf_enc
is the initalized state derived from
.Fn blf_key .
The stream of data is encrypted in Electronic Cookbook Mode (ECB) and
.Pa datalen
must be even.
.Fn blf_dec
is used for decrypting Blowfish encrypted blocks.
.Pp
The functions
.Fn Blowfish_initstate ,
.Fn Blowfish_expand0state ,
.Fn Blowfish_expandstate ,
.Fn Blowfish_encipher
and
.Fn Blowfish_decipher
are used for customization of the
.Pa Blowfish
cipher, i.e. for the blowfish password hashing function or for
implementation of Cipher Block Chaining Mode (CBC).
.Sh SEE ALSO
.Xr crypt 3 ,
.Xr passwd 1 ,
.Xr passwd 5
.Sh AUTHOR
Niels Provos <provos@physnet.uni-hamburg.de>