| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | 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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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/ec.h>
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| 10 |
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| 11 | const EC_METHOD *EC_GFp_simple_method(void);
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| 12 | const EC_METHOD *EC_GFp_mont_method(void);
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| 13 | const EC_METHOD *EC_GFp_nist_method(void);
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| 14 | const EC_METHOD *EC_GFp_nistp224_method(void);
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| 15 | const EC_METHOD *EC_GFp_nistp256_method(void);
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| 16 | const EC_METHOD *EC_GFp_nistp521_method(void);
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| 17 |
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| 18 | const EC_METHOD *EC_GF2m_simple_method(void);
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| 19 |
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| 20 | int EC_METHOD_get_field_type(const EC_METHOD *meth);
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| 21 |
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| 22 | =head1 DESCRIPTION
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| 23 |
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| 24 | The Elliptic Curve library provides a number of different implementations through a single common interface.
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| 25 | When constructing a curve using EC_GROUP_new (see L<EC_GROUP_new(3)>) an
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| 26 | implementation method must be provided. The functions described here all return a const pointer to an
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| 27 | B<EC_METHOD> structure that can be passed to EC_GROUP_NEW. It is important that the correct implementation
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| 28 | type for the form of curve selected is used.
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| 29 |
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| 30 | For F2^m curves there is only one implementation choice, i.e. EC_GF2_simple_method.
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| 31 |
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| 32 | For Fp curves the lowest common denominator implementation is the EC_GFp_simple_method implementation. All
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| 33 | other implementations are based on this one. EC_GFp_mont_method builds on EC_GFp_simple_method but adds the
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| 34 | use of montgomery multiplication (see L<BN_mod_mul_montgomery(3)>). EC_GFp_nist_method
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| 35 | offers an implementation optimised for use with NIST recommended curves (NIST curves are available through
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| 36 | EC_GROUP_new_by_curve_name as described in L<EC_GROUP_new(3)>).
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| 37 |
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| 38 | The functions EC_GFp_nistp224_method, EC_GFp_nistp256_method and EC_GFp_nistp521_method offer 64 bit
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| 39 | optimised implementations for the NIST P224, P256 and P521 curves respectively. Note, however, that these
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| 40 | implementations are not available on all platforms.
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| 41 |
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| 42 | EC_METHOD_get_field_type identifies what type of field the EC_METHOD structure supports, which will be either
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| 43 | 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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| 44 | F2^m then the value B<NID_X9_62_characteristic_two_field> is returned. These values are defined in the
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| 45 | obj_mac.h header file.
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| 46 |
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| 47 | =head1 RETURN VALUES
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| 48 |
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| 49 | All EC_GFp* functions and EC_GF2m_simple_method always return a const pointer to an EC_METHOD structure.
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| 50 |
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| 51 | EC_METHOD_get_field_type returns an integer that identifies the type of field the EC_METHOD structure supports.
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| 52 |
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| 53 | =head1 SEE ALSO
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| 54 |
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| 55 | L<crypto(7)>, L<EC_GROUP_new(3)>, L<EC_GROUP_copy(3)>,
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| 56 | L<EC_POINT_new(3)>, L<EC_POINT_add(3)>, L<EC_KEY_new(3)>,
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| 57 | L<d2i_ECPKParameters(3)>,
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| 58 | L<BN_mod_mul_montgomery(3)>
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| 59 |
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| 60 | =head1 COPYRIGHT
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| 61 |
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| 62 | Copyright 2013-2017 The OpenSSL Project Authors. All Rights Reserved.
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| 63 |
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| 64 | Licensed under the OpenSSL license (the "License"). You may not use
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| 65 | this file except in compliance with the License. You can obtain a copy
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| 66 | in the file LICENSE in the source distribution or at
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| 67 | L<https://www.openssl.org/source/license.html>.
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| 68 |
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| 69 | =cut
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