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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 mes-
sage. 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 proto-
cols 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 inte-
ger 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 encryp-
tion. 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.
0.9.8e-rhel5 2005-02-19 blowfish(3)
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On Apache/2.2.3 (CentOS)
Under GNU General Public License
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