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 a 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.
HISTORY
The Blowfish functions are available in all versions of SSLeay
and OpenSSL.
