252 lines
9.1 KiB
Groff
252 lines
9.1 KiB
Groff
.\" $NetBSD: openssl_blowfish.3,v 1.8 2003/07/24 14:16:50 itojun Exp $
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.\" ======================================================================
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.\"
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.IX Title "blowfish 3"
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.TH blowfish 3 "0.9.7b" "2002-01-22" "OpenSSL"
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.UC
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.SH "NAME"
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blowfish, BF_set_key, BF_encrypt, BF_decrypt, BF_ecb_encrypt, BF_cbc_encrypt,
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BF_cfb64_encrypt, BF_ofb64_encrypt, BF_options \- Blowfish encryption
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.SH "LIBRARY"
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libcrypto, -lcrypto
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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.Vb 1
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\& #include <openssl/blowfish.h>
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.Ve
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.Vb 1
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\& void BF_set_key(BF_KEY *key, int len, const unsigned char *data);
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.Ve
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.Vb 10
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\& void BF_ecb_encrypt(const unsigned char *in, unsigned char *out,
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\& BF_KEY *key, int enc);
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\& void BF_cbc_encrypt(const unsigned char *in, unsigned char *out,
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\& long length, BF_KEY *schedule, unsigned char *ivec, int enc);
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\& void BF_cfb64_encrypt(const unsigned char *in, unsigned char *out,
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\& long length, BF_KEY *schedule, unsigned char *ivec, int *num,
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\& int enc);
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\& void BF_ofb64_encrypt(const unsigned char *in, unsigned char *out,
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\& long length, BF_KEY *schedule, unsigned char *ivec, int *num);
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\& const char *BF_options(void);
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.Ve
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.Vb 2
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\& void BF_encrypt(BF_LONG *data,const BF_KEY *key);
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\& void BF_decrypt(BF_LONG *data,const BF_KEY *key);
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.Ve
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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This library implements the Blowfish cipher, which was invented and described
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by Counterpane (see http://www.counterpane.com/blowfish.html ).
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.PP
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Blowfish is a block cipher that operates on 64 bit (8 byte) blocks of data.
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It uses a variable size key, but typically, 128 bit (16 byte) keys are
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a considered good for strong encryption. Blowfish can be used in the same
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modes as \s-1DES\s0 (see des_modes(7)). Blowfish is currently one
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of the faster block ciphers. It is quite a bit faster than \s-1DES\s0, and much
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faster than \s-1IDEA\s0 or \s-1RC2\s0.
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.PP
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Blowfish consists of a key setup phase and the actual encryption or decryption
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phase.
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.PP
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\&\fIBF_set_key()\fR sets up the \fB\s-1BF_KEY\s0\fR \fBkey\fR using the \fBlen\fR bytes long key
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at \fBdata\fR.
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.PP
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\&\fIBF_ecb_encrypt()\fR is the basic Blowfish encryption and decryption function.
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It encrypts or decrypts the first 64 bits of \fBin\fR using the key \fBkey\fR,
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putting the result in \fBout\fR. \fBenc\fR decides if encryption (\fB\s-1BF_ENCRYPT\s0\fR)
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or decryption (\fB\s-1BF_DECRYPT\s0\fR) shall be performed. The vector pointed at by
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\&\fBin\fR and \fBout\fR must be 64 bits in length, no less. If they are larger,
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everything after the first 64 bits is ignored.
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.PP
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The mode functions \fIBF_cbc_encrypt()\fR, \fIBF_cfb64_encrypt()\fR and \fIBF_ofb64_encrypt()\fR
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all operate on variable length data. They all take an initialization vector
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\&\fBivec\fR which needs to be passed along into the next call of the same function
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for the same message. \fBivec\fR may be initialized with anything, but the
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recipient needs to know what it was initialized with, or it won't be able
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to decrypt. Some programs and protocols simplify this, like \s-1SSH\s0, where
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\&\fBivec\fR is simply initialized to zero.
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\&\fIBF_cbc_encrypt()\fR operates on data that is a multiple of 8 bytes long, while
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\&\fIBF_cfb64_encrypt()\fR and \fIBF_ofb64_encrypt()\fR are used to encrypt an variable
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number of bytes (the amount does not have to be an exact multiple of 8). The
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purpose of the latter two is to simulate stream ciphers, and therefore, they
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need the parameter \fBnum\fR, which is a pointer to an integer where the current
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offset in \fBivec\fR is stored between calls. This integer must be initialized
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to zero when \fBivec\fR is initialized.
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.PP
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\&\fIBF_cbc_encrypt()\fR is the Cipher Block Chaining function for Blowfish. It
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encrypts or decrypts the 64 bits chunks of \fBin\fR using the key \fBschedule\fR,
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putting the result in \fBout\fR. \fBenc\fR decides if encryption (\s-1BF_ENCRYPT\s0) or
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decryption (\s-1BF_DECRYPT\s0) shall be performed. \fBivec\fR must point at an 8 byte
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long initialization vector.
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.PP
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\&\fIBF_cfb64_encrypt()\fR is the \s-1CFB\s0 mode for Blowfish with 64 bit feedback.
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It encrypts or decrypts the bytes in \fBin\fR using the key \fBschedule\fR,
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putting the result in \fBout\fR. \fBenc\fR decides if encryption (\fB\s-1BF_ENCRYPT\s0\fR)
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or decryption (\fB\s-1BF_DECRYPT\s0\fR) shall be performed. \fBivec\fR must point at an
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8 byte long initialization vector. \fBnum\fR must point at an integer which must
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be initially zero.
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.PP
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\&\fIBF_ofb64_encrypt()\fR is the \s-1OFB\s0 mode for Blowfish with 64 bit feedback.
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It uses the same parameters as \fIBF_cfb64_encrypt()\fR, which must be initialized
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the same way.
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.PP
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\&\fIBF_encrypt()\fR and \fIBF_decrypt()\fR are the lowest level functions for Blowfish
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encryption. They encrypt/decrypt the first 64 bits of the vector pointed by
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\&\fBdata\fR, using the key \fBkey\fR. These functions should not be used unless you
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implement 'modes' of Blowfish. The alternative is to use \fIBF_ecb_encrypt()\fR.
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If you still want to use these functions, you should be aware that they take
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each 32\-bit chunk in host-byte order, which is little-endian on little-endian
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platforms and big-endian on big-endian ones.
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.SH "RETURN VALUES"
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.IX Header "RETURN VALUES"
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None of the functions presented here return any value.
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.SH "NOTE"
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.IX Header "NOTE"
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Applications should use the higher level functions
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EVP_EncryptInit(3) etc. instead of calling the
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blowfish functions directly.
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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des_modes(7)
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.SH "HISTORY"
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.IX Header "HISTORY"
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The Blowfish functions are available in all versions of SSLeay and OpenSSL.
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