blowfish, BF_set_key, BF_encrypt, BF_decrypt, BF_ecb_encrypt,
BF_cbc_encrypt, BF_cfb64_encrypt, BF_ofb64_encrypt, BF_options – Blow-
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,
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);
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 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
BF_set_key() sets up the BF_KEY key using the len bytes long key at
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,
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 ini-
tialized 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
BF_cbc_encrypt() is the Cipher Block Chaining function for Blowfish.
It encrypts or decrypts the 64 bits chunks of in using the key sched-
ule, 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 decryp-
tion (BF_DECRYPT) shall be performed. ivec must point at an 8 byte
long initialization vector. num must point at an integer which must be
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 ini-
tialized the same way.
BF_encrypt() and BF_decrypt() are the lowest level functions for Blow-
fish 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
None of the functions presented here return any value.
Applications should use the higher level functions EVP_EncryptInit(3)
etc. instead of calling the blowfish functions directly.