blowfish.pod 4.7 KB

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  1. =pod
  2. =head1 NAME
  3. blowfish, BF_set_key, BF_encrypt, BF_decrypt, BF_ecb_encrypt, BF_cbc_encrypt,
  4. BF_cfb64_encrypt, BF_ofb64_encrypt, BF_options - Blowfish encryption
  5. =head1 SYNOPSIS
  6. #include <openssl/blowfish.h>
  7. void BF_set_key(BF_KEY *key, int len, const unsigned char *data);
  8. void BF_ecb_encrypt(const unsigned char *in, unsigned char *out,
  9. BF_KEY *key, int enc);
  10. void BF_cbc_encrypt(const unsigned char *in, unsigned char *out,
  11. long length, BF_KEY *schedule, unsigned char *ivec, int enc);
  12. void BF_cfb64_encrypt(const unsigned char *in, unsigned char *out,
  13. long length, BF_KEY *schedule, unsigned char *ivec, int *num,
  14. int enc);
  15. void BF_ofb64_encrypt(const unsigned char *in, unsigned char *out,
  16. long length, BF_KEY *schedule, unsigned char *ivec, int *num);
  17. const char *BF_options(void);
  18. void BF_encrypt(BF_LONG *data,const BF_KEY *key);
  19. void BF_decrypt(BF_LONG *data,const BF_KEY *key);
  20. =head1 DESCRIPTION
  21. This library implements the Blowfish cipher, which was invented and described
  22. by Counterpane (see http://www.counterpane.com/blowfish.html ).
  23. Blowfish is a block cipher that operates on 64 bit (8 byte) blocks of data.
  24. It uses a variable size key, but typically, 128 bit (16 byte) keys are
  25. considered good for strong encryption. Blowfish can be used in the same
  26. modes as DES (see L<des_modes(7)|des_modes(7)>). Blowfish is currently one
  27. of the faster block ciphers. It is quite a bit faster than DES, and much
  28. faster than IDEA or RC2.
  29. Blowfish consists of a key setup phase and the actual encryption or decryption
  30. phase.
  31. BF_set_key() sets up the B<BF_KEY> B<key> using the B<len> bytes long key
  32. at B<data>.
  33. BF_ecb_encrypt() is the basic Blowfish encryption and decryption function.
  34. It encrypts or decrypts the first 64 bits of B<in> using the key B<key>,
  35. putting the result in B<out>. B<enc> decides if encryption (B<BF_ENCRYPT>)
  36. or decryption (B<BF_DECRYPT>) shall be performed. The vector pointed at by
  37. B<in> and B<out> must be 64 bits in length, no less. If they are larger,
  38. everything after the first 64 bits is ignored.
  39. The mode functions BF_cbc_encrypt(), BF_cfb64_encrypt() and BF_ofb64_encrypt()
  40. all operate on variable length data. They all take an initialization vector
  41. B<ivec> which needs to be passed along into the next call of the same function
  42. for the same message. B<ivec> may be initialized with anything, but the
  43. recipient needs to know what it was initialized with, or it won't be able
  44. to decrypt. Some programs and protocols simplify this, like SSH, where
  45. B<ivec> is simply initialized to zero.
  46. BF_cbc_encrypt() operates on data that is a multiple of 8 bytes long, while
  47. BF_cfb64_encrypt() and BF_ofb64_encrypt() are used to encrypt an variable
  48. number of bytes (the amount does not have to be an exact multiple of 8). The
  49. purpose of the latter two is to simulate stream ciphers, and therefore, they
  50. need the parameter B<num>, which is a pointer to an integer where the current
  51. offset in B<ivec> is stored between calls. This integer must be initialized
  52. to zero when B<ivec> is initialized.
  53. BF_cbc_encrypt() is the Cipher Block Chaining function for Blowfish. It
  54. encrypts or decrypts the 64 bits chunks of B<in> using the key B<schedule>,
  55. putting the result in B<out>. B<enc> decides if encryption (BF_ENCRYPT) or
  56. decryption (BF_DECRYPT) shall be performed. B<ivec> must point at an 8 byte
  57. long initialization vector.
  58. BF_cfb64_encrypt() is the CFB mode for Blowfish with 64 bit feedback.
  59. It encrypts or decrypts the bytes in B<in> using the key B<schedule>,
  60. putting the result in B<out>. B<enc> decides if encryption (B<BF_ENCRYPT>)
  61. or decryption (B<BF_DECRYPT>) shall be performed. B<ivec> must point at an
  62. 8 byte long initialization vector. B<num> must point at an integer which must
  63. be initially zero.
  64. BF_ofb64_encrypt() is the OFB mode for Blowfish with 64 bit feedback.
  65. It uses the same parameters as BF_cfb64_encrypt(), which must be initialized
  66. the same way.
  67. BF_encrypt() and BF_decrypt() are the lowest level functions for Blowfish
  68. encryption. They encrypt/decrypt the first 64 bits of the vector pointed by
  69. B<data>, using the key B<key>. These functions should not be used unless you
  70. implement 'modes' of Blowfish. The alternative is to use BF_ecb_encrypt().
  71. If you still want to use these functions, you should be aware that they take
  72. each 32-bit chunk in host-byte order, which is little-endian on little-endian
  73. platforms and big-endian on big-endian ones.
  74. =head1 RETURN VALUES
  75. None of the functions presented here return any value.
  76. =head1 NOTE
  77. Applications should use the higher level functions
  78. L<EVP_EncryptInit(3)|EVP_EncryptInit(3)> etc. instead of calling the
  79. blowfish functions directly.
  80. =head1 SEE ALSO
  81. L<des_modes(7)|des_modes(7)>
  82. =head1 HISTORY
  83. The Blowfish functions are available in all versions of SSLeay and OpenSSL.
  84. =cut