Blowfish docs.

doc/crypto/blowfish.pod

+=pod
+
+=head1 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
+
+=head1 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);
+ const char *BF_options(void);
+
+=head1 DESCRIPTION
+
+This library implements the Blowfish cipher, which is invented and described
+by Counterpane (see http://www.counterpane.com/blowfish/ ).
+
+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 L<des_modes(7)|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 B<BF_KEY> B<key> using the B<len> bytes long key
+at B<data>.
+
+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
+B<data>, using the key B<key>.  These functions should not be used unless you
+implement 'modes' of Blowfish.
+
+BF_ecb_encrypt() is the basic Blowfish encryption and decryption function.
+It encrypts or decrypts the first 64 bits of B<in> using the key B<key>,
+putting the result in B<out>.  B<enc> decides if encryption (B<BF_ENCRYPT>)
+or decryption (B<BF_DECRYPT>) shall be performed.  The vector pointed at by
+B<in> and B<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 initialisation vector
+B<ivec> which must be initially filled with zeros, but then just need to be
+passed along into the next call of the same function for the same message. 
+BF_cbc_encrypt() operates of 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 B<num>, which is a pointer to an integer where the current
+offset in B<ivec> is stored between calls.  This integer must be initialised
+to zero when B<ivec> is filled with zeros.
+
+BF_cbc_encrypt() is the Cipher Block Chaining function for Blowfish.  It
+encrypts or decrypts the 64 bits chunks of B<in> using the key B<schedule>,
+putting the result in B<out>.  B<enc> decides if encryption (BF_ENCRYPT) or
+decryption (BF_DECRYPT) shall be performed.  B<ivec> must point at an 8 byte
+long initialisation vector, which must be initially filled with zeros.
+
+BF_cfb64_encrypt() is the CFB mode for Blowfish with 64 bit feedback.
+It encrypts or decrypts the bytes in B<in> using the key B<schedule>,
+putting the result in B<out>.  B<enc> decides if encryption (B<BF_ENCRYPT>)
+or decryption (B<BF_DECRYPT>) shall be performed.  B<ivec> must point at an
+8 byte long initialisation vector, which must be initially filled with zeros.
+B<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 initialised
+the same way.
+
+=head1 RETURN VALUES
+
+None of the functions presented here return any value.
+
+=head1 NOTE
+
+Applications should use the higher level functions EVP_DigestInit(3) etc.
+instead of calling the blowfish functions directly.
+
+=head1 SEE ALSO
+
+L<des_modes(7)|des_modes(7)>
+
+=head1 HISTORY
+
+The Blowfish functions are available in all versions of SSLeay and OpenSSL.
+
+=cut
+