BF_SET_KEY(3) BSD Library Functions Manual BF_SET_KEY(3)NAME
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.
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(3)). 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 func‐
tion. 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, every‐
thing 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 sim‐
plify 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 multi‐
ple 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 ini‐
tialization 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.
BSD July 17, 2014 BSD
