mirror of https://github.com/openssl/openssl
207 lines
8.0 KiB
Plaintext
207 lines
8.0 KiB
Plaintext
=pod
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=head1 NAME
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EC_GROUP_get_ecparameters,
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EC_GROUP_get_ecpkparameters,
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EC_GROUP_new,
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EC_GROUP_new_from_ecparameters,
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EC_GROUP_new_from_ecpkparameters,
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EC_GROUP_free,
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EC_GROUP_clear_free,
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EC_GROUP_new_curve_GFp,
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EC_GROUP_new_curve_GF2m,
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EC_GROUP_new_by_curve_name_with_libctx,
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EC_GROUP_new_by_curve_name,
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EC_GROUP_set_curve,
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EC_GROUP_get_curve,
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EC_GROUP_set_curve_GFp,
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EC_GROUP_get_curve_GFp,
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EC_GROUP_set_curve_GF2m,
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EC_GROUP_get_curve_GF2m,
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EC_get_builtin_curves - Functions for creating and destroying EC_GROUP
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objects
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=head1 SYNOPSIS
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#include <openssl/ec.h>
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EC_GROUP *EC_GROUP_new_from_ecparameters(const ECPARAMETERS *params)
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EC_GROUP *EC_GROUP_new_from_ecpkparameters(const ECPKPARAMETERS *params)
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void EC_GROUP_free(EC_GROUP *group);
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EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a,
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const BIGNUM *b, BN_CTX *ctx);
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EC_GROUP *EC_GROUP_new_curve_GF2m(const BIGNUM *p, const BIGNUM *a,
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const BIGNUM *b, BN_CTX *ctx);
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EC_GROUP *EC_GROUP_new_by_curve_name_with_libctx(OPENSSL_CTX *libctx,
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const char *propq, int nid);
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EC_GROUP *EC_GROUP_new_by_curve_name(int nid);
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int EC_GROUP_set_curve(EC_GROUP *group, const BIGNUM *p, const BIGNUM *a,
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const BIGNUM *b, BN_CTX *ctx);
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int EC_GROUP_get_curve(const EC_GROUP *group, BIGNUM *p, BIGNUM *a, BIGNUM *b,
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BN_CTX *ctx);
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int EC_GROUP_set_curve_GFp(EC_GROUP *group, const BIGNUM *p,
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const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx);
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int EC_GROUP_get_curve_GFp(const EC_GROUP *group, BIGNUM *p,
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BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
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int EC_GROUP_set_curve_GF2m(EC_GROUP *group, const BIGNUM *p,
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const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx);
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int EC_GROUP_get_curve_GF2m(const EC_GROUP *group, BIGNUM *p,
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BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
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ECPARAMETERS *EC_GROUP_get_ecparameters(const EC_GROUP *group, ECPARAMETERS *params)
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ECPKPARAMETERS *EC_GROUP_get_ecpkparameters(const EC_GROUP *group, ECPKPARAMETERS *params)
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size_t EC_get_builtin_curves(EC_builtin_curve *r, size_t nitems);
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Deprecated since OpenSSL 3.0, can be hidden entirely by defining
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B<OPENSSL_API_COMPAT> with a suitable version value, see
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L<openssl_user_macros(7)>:
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EC_GROUP *EC_GROUP_new(const EC_METHOD *meth);
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void EC_GROUP_clear_free(EC_GROUP *group);
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=head1 DESCRIPTION
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Within the library there are two forms of elliptic curve that are of interest.
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The first form is those defined over the prime field Fp. The elements of Fp are
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the integers 0 to p-1, where p is a prime number. This gives us a revised
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elliptic curve equation as follows:
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y^2 mod p = x^3 +ax + b mod p
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The second form is those defined over a binary field F2^m where the elements of
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the field are integers of length at most m bits. For this form the elliptic
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curve equation is modified to:
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y^2 + xy = x^3 + ax^2 + b (where b != 0)
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Operations in a binary field are performed relative to an
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B<irreducible polynomial>. All such curves with OpenSSL use a trinomial or a
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pentanomial for this parameter.
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Although deprecated since OpenSSL 3.0 and should no longer be used,
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a new curve can be constructed by calling EC_GROUP_new(), using the
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implementation provided by I<meth> (see L<EC_GFp_simple_method(3)>) and
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associated with the library context I<ctx> (see L<OPENSSL_CTX(3)>).
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The I<ctx> parameter may be NULL in which case the default library context is
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used.
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It is then necessary to call EC_GROUP_set_curve() to set the curve parameters.
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Applications should instead use one of the other EC_GROUP_new_* constructors.
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EC_GROUP_new_from_ecparameters() will create a group from the
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specified I<params> and
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EC_GROUP_new_from_ecpkparameters() will create a group from the specific PK
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I<params>.
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EC_GROUP_set_curve() sets the curve parameters I<p>, I<a> and I<b>. For a curve
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over Fp I<p> is the prime for the field. For a curve over F2^m I<p> represents
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the irreducible polynomial - each bit represents a term in the polynomial.
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Therefore, there will either be three or five bits set dependent on whether the
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polynomial is a trinomial or a pentanomial.
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In either case, I<a> and I<b> represents the coefficients a and b from the
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relevant equation introduced above.
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EC_group_get_curve() obtains the previously set curve parameters.
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EC_GROUP_set_curve_GFp() and EC_GROUP_set_curve_GF2m() are synonyms for
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EC_GROUP_set_curve(). They are defined for backwards compatibility only and
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should not be used.
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EC_GROUP_get_curve_GFp() and EC_GROUP_get_curve_GF2m() are synonyms for
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EC_GROUP_get_curve(). They are defined for backwards compatibility only and
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should not be used.
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The functions EC_GROUP_new_curve_GFp() and EC_GROUP_new_curve_GF2m() are
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shortcuts for calling EC_GROUP_new() and then the EC_GROUP_set_curve() function.
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An appropriate default implementation method will be used.
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Whilst the library can be used to create any curve using the functions described
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above, there are also a number of predefined curves that are available. In order
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to obtain a list of all of the predefined curves, call the function
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EC_get_builtin_curves(). The parameter I<r> should be an array of
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EC_builtin_curve structures of size I<nitems>. The function will populate the
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I<r> array with information about the built-in curves. If I<nitems> is less than
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the total number of curves available, then the first I<nitems> curves will be
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returned. Otherwise the total number of curves will be provided. The return
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value is the total number of curves available (whether that number has been
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populated in I<r> or not). Passing a NULL I<r>, or setting I<nitems> to 0 will
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do nothing other than return the total number of curves available.
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The EC_builtin_curve structure is defined as follows:
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typedef struct {
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int nid;
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const char *comment;
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} EC_builtin_curve;
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Each EC_builtin_curve item has a unique integer id (I<nid>), and a human
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readable comment string describing the curve.
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In order to construct a built-in curve use the function
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EC_GROUP_new_by_curve_name_with_libctx() and provide the I<nid> of the curve to
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be constructed, the associated library context to be used in I<ctx> (see
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L<OPENSSL_CTX(3)>) and any property query string in I<propq>. The I<ctx> value
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may be NULL in which case the default library context is used. The I<propq>
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value may also be NULL.
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EC_GROUP_new_by_curve_name() is the same as
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EC_GROUP_new_by_curve_name_with_libctx() except that the default library context
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is always used along with a NULL property query string.
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EC_GROUP_free() frees the memory associated with the EC_GROUP.
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If I<group> is NULL nothing is done.
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EC_GROUP_clear_free() is deprecated: it was meant to destroy any sensitive data
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held within the EC_GROUP and then free its memory, but since all the data stored
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in the EC_GROUP is public anyway, this function is unnecessary.
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Its use can be safely replaced with EC_GROUP_free().
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If I<group> is NULL nothing is done.
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=head1 RETURN VALUES
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All EC_GROUP_new* functions return a pointer to the newly constructed group, or
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NULL on error.
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EC_get_builtin_curves() returns the number of built-in curves that are
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available.
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EC_GROUP_set_curve_GFp(), EC_GROUP_get_curve_GFp(), EC_GROUP_set_curve_GF2m(),
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EC_GROUP_get_curve_GF2m() return 1 on success or 0 on error.
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=head1 SEE ALSO
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L<crypto(7)>, 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<EC_GFp_simple_method(3)>, L<d2i_ECPKParameters(3)>,
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L<OPENSSL_CTX(3)>
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=head1 HISTORY
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=over 2
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=item *
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EC_GROUP_new() was deprecated in OpenSSL 3.0.
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EC_GROUP_new_by_curve_name_with_libctx() was added in OpenSSL 3.0.
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=item *
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EC_GROUP_clear_free() was deprecated in OpenSSL 3.0; use EC_GROUP_free()
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instead.
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=back
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=head1 COPYRIGHT
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Copyright 2013-2020 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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