evp - high-level…

# Blowfish

blowfish, BF_set_key, BF_encrypt, BF_decrypt, BF_ecb_encrypt,

BF_cbc_encrypt, BF_cfb64_encrypt, BF_ofb64_encrypt, BF_options – Blow-

fish 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 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 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

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 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

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 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

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.

**EOF**