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4746f25ac6
[skip ci] Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7829)
70 lines
3.0 KiB
Plaintext
70 lines
3.0 KiB
Plaintext
=pod
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=head1 NAME
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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
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=head1 SYNOPSIS
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#include <openssl/ec.h>
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const EC_METHOD *EC_GFp_simple_method(void);
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const EC_METHOD *EC_GFp_mont_method(void);
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const EC_METHOD *EC_GFp_nist_method(void);
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const EC_METHOD *EC_GFp_nistp224_method(void);
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const EC_METHOD *EC_GFp_nistp256_method(void);
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const EC_METHOD *EC_GFp_nistp521_method(void);
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const EC_METHOD *EC_GF2m_simple_method(void);
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int EC_METHOD_get_field_type(const EC_METHOD *meth);
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=head1 DESCRIPTION
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The Elliptic Curve library provides a number of different implementations through a single common interface.
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When constructing a curve using EC_GROUP_new (see L<EC_GROUP_new(3)>) an
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implementation method must be provided. The functions described here all return a const pointer to an
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B<EC_METHOD> structure that can be passed to EC_GROUP_NEW. It is important that the correct implementation
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type for the form of curve selected is used.
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For F2^m curves there is only one implementation choice, i.e. EC_GF2_simple_method.
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For Fp curves the lowest common denominator implementation is the EC_GFp_simple_method implementation. All
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other implementations are based on this one. EC_GFp_mont_method builds on EC_GFp_simple_method but adds the
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use of montgomery multiplication (see L<BN_mod_mul_montgomery(3)>). EC_GFp_nist_method
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offers an implementation optimised for use with NIST recommended curves (NIST curves are available through
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EC_GROUP_new_by_curve_name as described in L<EC_GROUP_new(3)>).
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The functions EC_GFp_nistp224_method, EC_GFp_nistp256_method and EC_GFp_nistp521_method offer 64 bit
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optimised implementations for the NIST P224, P256 and P521 curves respectively. Note, however, that these
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implementations are not available on all platforms.
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EC_METHOD_get_field_type identifies what type of field the EC_METHOD structure supports, which will be either
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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
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F2^m then the value B<NID_X9_62_characteristic_two_field> is returned. These values are defined in the
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obj_mac.h header file.
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=head1 RETURN VALUES
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All EC_GFp* functions and EC_GF2m_simple_method always return a const pointer to an EC_METHOD structure.
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EC_METHOD_get_field_type returns an integer that identifies the type of field the EC_METHOD structure supports.
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=head1 SEE ALSO
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L<crypto(7)>, L<EC_GROUP_new(3)>, L<EC_GROUP_copy(3)>,
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L<EC_POINT_new(3)>, L<EC_POINT_add(3)>, L<EC_KEY_new(3)>,
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L<d2i_ECPKParameters(3)>,
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L<BN_mod_mul_montgomery(3)>
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=head1 COPYRIGHT
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Copyright 2013-2017 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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