NAME
BF_set_key,
BF_encrypt, BF_decrypt,
BF_ecb_encrypt,
BF_cbc_encrypt,
BF_cfb64_encrypt,
BF_ofb64_encrypt —
Blowfish encryption
SYNOPSIS
#include
<openssl/blowfish.h>
void
BF_set_key(BF_KEY *key,
int len, const unsigned char
*data);
void
BF_encrypt(BF_LONG *data,
const BF_KEY *key);
void
BF_decrypt(BF_LONG *data,
const BF_KEY *key);
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);
DESCRIPTION
This library implements the Blowfish cipher, which was invented and defined by Counterpane. Note that applications should use higher level functions such as EVP_EncryptInit(3) instead of calling the Blowfish functions directly.
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 and 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 a 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-bit 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
implementing `modes' of Blowfish. The alternative is to use
BF_ecb_encrypt(). Be aware that these functions take
each 32-bit chunk in host-byte order, which is little-endian on
little-endian platforms and big-endian on big-endian ones.
SEE ALSO
HISTORY
BF_set_key(),
BF_encrypt(),
BF_ecb_encrypt(),
BF_cbc_encrypt(),
BF_cfb64_encrypt(), and
BF_ofb64_encrypt() first appeared in SSLeay 0.6.6.
BF_decrypt() first appeared in SSLeay 0.9.0. All
these functions have been available since OpenBSD
2.4.