.\" $OpenBSD: blowfish.3,v 1.20 2007/05/31 19:19:27 jmc Exp $
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.\" Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
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.\" Manual page, using -mandoc macros
.\"
.Dd $Mdocdate: May 31 2007 $
.Dt BLOWFISH 3
.Os
.Sh NAME
.Nm blf_key ,
.Nm blf_enc ,
.Nm blf_dec ,
.Nm blf_ecb_encrypt ,
.Nm blf_ecb_decrypt ,
.Nm blf_cbc_encrypt ,
.Nm blf_cbc_decrypt
.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 blocks"
.Ft void
.Fn blf_dec "blf_ctx *state" "u_int32_t *data" "u_int16_t blocks"
.Ft void
.Fn blf_ecb_encrypt "blf_ctx *state" "u_int8_t *data" "u_int32_t datalen"
.Ft void
.Fn blf_ecb_decrypt "blf_ctx *state" "u_int8_t *data" "u_int32_t datalen"
.Ft void
.Fn blf_cbc_encrypt "blf_ctx *state" "u_int8_t *iv" "u_int8_t *data" "u_int32_t datalen"
.Ft void
.Fn blf_cbc_decrypt "blf_ctx *state" "u_int8_t *iv" "u_int8_t *data" "u_int32_t datalen"
.Sh DESCRIPTION
.Em Blowfish
is a fast unpatented block cipher designed by Bruce Schneier.
It basically consists of a 16-round Feistel network.
The block size is 64 bits and the maximum key size is 448 bits.
.Pp
The
.Fn blf_key
function initializes the 4 8-bit 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 initialized state derived from
.Fn blf_key .
The stream of 32-bit words is encrypted in Electronic Codebook
Mode (ECB) and
.Fa blocks
is the number of 64-bit blocks in the stream.
.Fn blf_dec
is used for decrypting Blowfish encrypted blocks.
.Pp
The functions
.Fn blf_ecb_encrypt
and
.Fn blf_ecb_decrypt
are used for encrypting and decrypting octet streams in ECB mode.
The functions
.Fn blf_cbc_encrypt
and
.Fn blf_cbc_decrypt
are used for encrypting and decrypting octet streams in
Cipherblock Chaining Mode (CBC).
For these functions
.Fa datalen
specifies the number of octets of data to encrypt or decrypt.
It must be a multiple of 8 (64-bit block).
The initialisation vector
.Fa iv
points to an 8-byte buffer.
.Sh SEE ALSO
.Xr passwd 1 ,
.Xr crypt 3 ,
.Xr passwd 5
.Sh AUTHORS
.An Niels Provos Aq provos@physnet.uni-hamburg.de