mirror of
https://github.com/openssl/openssl.git
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b97fdb57a2
Reviewed-by: Rich Salz <rsalz@openssl.org> (Merged from https://github.com/openssl/openssl/pull/1900)
77 lines
2.2 KiB
Plaintext
77 lines
2.2 KiB
Plaintext
=pod
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=head1 NAME
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BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new,
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BN_RECP_CTX_free, BN_RECP_CTX_set - modular multiplication using
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reciprocal
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=head1 SYNOPSIS
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#include <openssl/bn.h>
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BN_RECP_CTX *BN_RECP_CTX_new(void);
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void BN_RECP_CTX_free(BN_RECP_CTX *recp);
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int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *m, BN_CTX *ctx);
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int BN_div_recp(BIGNUM *dv, BIGNUM *rem, BIGNUM *a, BN_RECP_CTX *recp,
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BN_CTX *ctx);
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int BN_mod_mul_reciprocal(BIGNUM *r, BIGNUM *a, BIGNUM *b,
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BN_RECP_CTX *recp, BN_CTX *ctx);
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=head1 DESCRIPTION
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BN_mod_mul_reciprocal() can be used to perform an efficient
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L<BN_mod_mul(3)> operation when the operation will be performed
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repeatedly with the same modulus. It computes B<r>=(B<a>*B<b>)%B<m>
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using B<recp>=1/B<m>, which is set as described below. B<ctx> is a
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previously allocated B<BN_CTX> used for temporary variables.
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BN_RECP_CTX_new() allocates and initializes a B<BN_RECP> structure.
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BN_RECP_CTX_free() frees the components of the B<BN_RECP>, and, if it
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was created by BN_RECP_CTX_new(), also the structure itself.
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If B<recp> is NULL, nothing is done.
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BN_RECP_CTX_set() stores B<m> in B<recp> and sets it up for computing
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1/B<m> and shifting it left by BN_num_bits(B<m>)+1 to make it an
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integer. The result and the number of bits it was shifted left will
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later be stored in B<recp>.
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BN_div_recp() divides B<a> by B<m> using B<recp>. It places the quotient
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in B<dv> and the remainder in B<rem>.
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The B<BN_RECP_CTX> structure cannot be shared between threads.
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=head1 RETURN VALUES
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BN_RECP_CTX_new() returns the newly allocated B<BN_RECP_CTX>, and NULL
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on error.
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BN_RECP_CTX_free() has no return value.
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For the other functions, 1 is returned for success, 0 on error.
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The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 SEE ALSO
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L<bn(7)>, L<ERR_get_error(3)>, L<BN_add(3)>,
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L<BN_CTX_new(3)>
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=head1 HISTORY
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BN_RECP_CTX_init() was removed in OpenSSL 1.1.0
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=head1 COPYRIGHT
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Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (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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