112 lines
4.7 KiB
Text
112 lines
4.7 KiB
Text
=pod
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=head1 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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=head1 SYNOPSIS
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#include <openssl/blowfish.h>
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void BF_set_key(BF_KEY *key, int len, const unsigned char *data);
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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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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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=head1 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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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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considered good for strong encryption. Blowfish can be used in the same
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modes as DES (see L<des_modes(7)|des_modes(7)>). Blowfish is currently one
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of the faster block ciphers. It is quite a bit faster than DES, and much
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faster than IDEA or RC2.
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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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BF_set_key() sets up the B<BF_KEY> B<key> using the B<len> bytes long key
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at B<data>.
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BF_ecb_encrypt() is the basic Blowfish encryption and decryption function.
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It encrypts or decrypts the first 64 bits of B<in> using the key B<key>,
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putting the result in B<out>. B<enc> decides if encryption (B<BF_ENCRYPT>)
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or decryption (B<BF_DECRYPT>) shall be performed. The vector pointed at by
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B<in> and B<out> 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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The mode functions BF_cbc_encrypt(), BF_cfb64_encrypt() and BF_ofb64_encrypt()
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all operate on variable length data. They all take an initialization vector
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B<ivec> which needs to be passed along into the next call of the same function
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for the same message. B<ivec> 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 SSH, where
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B<ivec> is simply initialized to zero.
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BF_cbc_encrypt() operates on data that is a multiple of 8 bytes long, while
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BF_cfb64_encrypt() and BF_ofb64_encrypt() 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 B<num>, which is a pointer to an integer where the current
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offset in B<ivec> is stored between calls. This integer must be initialized
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to zero when B<ivec> is initialized.
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BF_cbc_encrypt() is the Cipher Block Chaining function for Blowfish. It
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encrypts or decrypts the 64 bits chunks of B<in> using the key B<schedule>,
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putting the result in B<out>. B<enc> decides if encryption (BF_ENCRYPT) or
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decryption (BF_DECRYPT) shall be performed. B<ivec> must point at an 8 byte
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long initialization vector.
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BF_cfb64_encrypt() is the CFB mode for Blowfish with 64 bit feedback.
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It encrypts or decrypts the bytes in B<in> using the key B<schedule>,
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putting the result in B<out>. B<enc> decides if encryption (B<BF_ENCRYPT>)
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or decryption (B<BF_DECRYPT>) shall be performed. B<ivec> must point at an
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8 byte long initialization vector. B<num> must point at an integer which must
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be initially zero.
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BF_ofb64_encrypt() is the OFB mode for Blowfish with 64 bit feedback.
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It uses the same parameters as BF_cfb64_encrypt(), which must be initialized
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the same way.
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BF_encrypt() and BF_decrypt() 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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B<data>, using the key B<key>. These functions should not be used unless you
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implement 'modes' of Blowfish. The alternative is to use BF_ecb_encrypt().
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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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=head1 RETURN VALUES
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None of the functions presented here return any value.
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=head1 NOTE
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Applications should use the higher level functions
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L<EVP_EncryptInit(3)|EVP_EncryptInit(3)> etc. instead of calling the
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blowfish functions directly.
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=head1 SEE ALSO
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L<des_modes(7)|des_modes(7)>
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=head1 HISTORY
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The Blowfish functions are available in all versions of SSLeay and OpenSSL.
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=cut
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