EC_GFp_simple_method.pod 3.0 KB

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  1. =pod
  2. =head1 NAME
  3. EC_GFp_simple_method, EC_GFp_mont_method, EC_GFp_nist_method, EC_GFp_nistp224_method, EC_GFp_nistp256_method, EC_GFp_nistp521_method, EC_GF2m_simple_method, EC_METHOD_get_field_type - Functions for obtaining EC_METHOD objects
  4. =head1 SYNOPSIS
  5. #include <openssl/ec.h>
  6. const EC_METHOD *EC_GFp_simple_method(void);
  7. const EC_METHOD *EC_GFp_mont_method(void);
  8. const EC_METHOD *EC_GFp_nist_method(void);
  9. const EC_METHOD *EC_GFp_nistp224_method(void);
  10. const EC_METHOD *EC_GFp_nistp256_method(void);
  11. const EC_METHOD *EC_GFp_nistp521_method(void);
  12. const EC_METHOD *EC_GF2m_simple_method(void);
  13. int EC_METHOD_get_field_type(const EC_METHOD *meth);
  14. =head1 DESCRIPTION
  15. The Elliptic Curve library provides a number of different implementations through a single common interface.
  16. When constructing a curve using EC_GROUP_new (see L<EC_GROUP_new(3)>) an
  17. implementation method must be provided. The functions described here all return a const pointer to an
  18. B<EC_METHOD> structure that can be passed to EC_GROUP_NEW. It is important that the correct implementation
  19. type for the form of curve selected is used.
  20. For F2^m curves there is only one implementation choice, i.e. EC_GF2_simple_method.
  21. For Fp curves the lowest common denominator implementation is the EC_GFp_simple_method implementation. All
  22. other implementations are based on this one. EC_GFp_mont_method builds on EC_GFp_simple_method but adds the
  23. use of montgomery multiplication (see L<BN_mod_mul_montgomery(3)>). EC_GFp_nist_method
  24. offers an implementation optimised for use with NIST recommended curves (NIST curves are available through
  25. EC_GROUP_new_by_curve_name as described in L<EC_GROUP_new(3)>).
  26. The functions EC_GFp_nistp224_method, EC_GFp_nistp256_method and EC_GFp_nistp521_method offer 64 bit
  27. optimised implementations for the NIST P224, P256 and P521 curves respectively. Note, however, that these
  28. implementations are not available on all platforms.
  29. EC_METHOD_get_field_type identifies what type of field the EC_METHOD structure supports, which will be either
  30. F2^m or Fp. If the field type is Fp then the value B<NID_X9_62_prime_field> is returned. If the field type is
  31. F2^m then the value B<NID_X9_62_characteristic_two_field> is returned. These values are defined in the
  32. obj_mac.h header file.
  33. =head1 RETURN VALUES
  34. All EC_GFp* functions and EC_GF2m_simple_method always return a const pointer to an EC_METHOD structure.
  35. EC_METHOD_get_field_type returns an integer that identifies the type of field the EC_METHOD structure supports.
  36. =head1 SEE ALSO
  37. L<crypto(7)>, L<EC_GROUP_new(3)>, L<EC_GROUP_copy(3)>,
  38. L<EC_POINT_new(3)>, L<EC_POINT_add(3)>, L<EC_KEY_new(3)>,
  39. L<d2i_ECPKParameters(3)>,
  40. L<BN_mod_mul_montgomery(3)>
  41. =head1 COPYRIGHT
  42. Copyright 2013-2017 The OpenSSL Project Authors. All Rights Reserved.
  43. Licensed under the Apache License 2.0 (the "License"). You may not use
  44. this file except in compliance with the License. You can obtain a copy
  45. in the file LICENSE in the source distribution or at
  46. L<https://www.openssl.org/source/license.html>.
  47. =cut