blowfish(3) OpenSSL blowfish(3)
NAME
blowfish, BF_set_key, BF_encrypt, BF_decrypt, BF_ecb_encrypt, BF_cbc_encrypt, BF_cfb64_encrypt,
BF_ofb64_encrypt, BF_options - Blowfish encryption
SYNOPSIS
#include <openssl/blowfish.h>
void BF_set_key(BF_KEY *key, int len, const unsigned char *data);
void BF_ecb_encrypt(const unsigned char *in, unsigned char *out,
BF_KEY *key, int enc);
void BF_cbc_encrypt(const unsigned char *in, unsigned char *out,
long length, BF_KEY *schedule, unsigned char *ivec, int enc);
void BF_cfb64_encrypt(const unsigned char *in, unsigned char *out,
long length, BF_KEY *schedule, unsigned char *ivec, int *num,
int enc);
void BF_ofb64_encrypt(const unsigned char *in, unsigned char *out,
long length, BF_KEY *schedule, unsigned char *ivec, int *num);
const char *BF_options(void);
void BF_encrypt(BF_LONG *data,const BF_KEY *key);
void BF_decrypt(BF_LONG *data,const BF_KEY *key);
DESCRIPTION
This library implements the Blowfish cipher, which was invented and described by Counterpane (see
http://www.counterpane.com/blowfish.html ).
Blowfish is a block cipher that operates on 64 bit (8 byte) blocks of data. It uses a variable size
key, but typically, 128 bit (16 byte) keys are considered good for strong encryption. Blowfish can
be used in the same modes as DES (see des_modes(7)). Blowfish is currently one of the faster block
ciphers. It is quite a bit faster than DES, and much faster than IDEA or RC2.
Blowfish consists of a key setup phase and the actual encryption or decryption phase.
BF_set_key() sets up the BF_KEY key using the len bytes long key at data.
BF_ecb_encrypt() is the basic Blowfish encryption and decryption function. It encrypts or decrypts
the first 64 bits of in using the key key, putting the result in out. enc decides if encryption
(BF_ENCRYPT) or decryption (BF_DECRYPT) shall be performed. The vector pointed at by in and out must
be 64 bits in length, no less. If they are larger, everything after the first 64 bits is ignored.
The mode functions BF_cbc_encrypt(), BF_cfb64_encrypt() and BF_ofb64_encrypt() all operate on
variable length data. They all take an initialization vector ivec which needs to be passed along
into the next call of the same function for the same message. ivec may be initialized with anything,
but the recipient needs to know what it was initialized with, or it won't be able to decrypt. Some
programs and protocols simplify this, like SSH, where ivec is simply initialized to zero.
BF_cbc_encrypt() operates on data that is a multiple of 8 bytes long, while BF_cfb64_encrypt() and
BF_ofb64_encrypt() are used to encrypt an variable number of bytes (the amount does not have to be an
exact multiple of 8). The purpose of the latter two is to simulate stream ciphers, and therefore,
they need the parameter num, which is a pointer to an integer where the current offset in ivec is
stored between calls. This integer must be initialized to zero when ivec is initialized.
BF_cbc_encrypt() is the Cipher Block Chaining function for Blowfish. It encrypts or decrypts the 64
bits chunks of in using the key schedule, putting the result in out. enc decides if encryption
(BF_ENCRYPT) or decryption (BF_DECRYPT) shall be performed. ivec must point at an 8 byte long
initialization vector.
BF_cfb64_encrypt() is the CFB mode for Blowfish with 64 bit feedback. It encrypts or decrypts the
bytes in in using the key schedule, putting the result in out. enc decides if encryption
(BF_ENCRYPT) or decryption (BF_DECRYPT) shall be performed. ivec must point at an 8 byte long
initialization vector. num must point at an integer which must be initially zero.
BF_ofb64_encrypt() is the OFB mode for Blowfish with 64 bit feedback. It uses the same parameters as
BF_cfb64_encrypt(), which must be initialized the same way.
BF_encrypt() and BF_decrypt() are the lowest level functions for Blowfish encryption. They
encrypt/decrypt the first 64 bits of the vector pointed by data, using the key key. These functions
should not be used unless you implement 'modes' of Blowfish. The alternative is to use
BF_ecb_encrypt(). If you still want to use these functions, you should be aware that they take each
32-bit chunk in host-byte order, which is little-endian on little-endian platforms and big-endian on
big-endian ones.
RETURN VALUES
None of the functions presented here return any value.
NOTE
Applications should use the higher level functions EVP_EncryptInit(3) etc. instead of calling the
blowfish functions directly.
SEE ALSO
des_modes(7)
HISTORY
The Blowfish functions are available in all versions of SSLeay and OpenSSL.
0.9.7l 2005-02-19 blowfish(3)
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