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dd8dec69 UM |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
0517ffc4 | 5 | BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, |
4d524e10 | 6 | BN_RECP_CTX_free, BN_RECP_CTX_set - modular multiplication using |
dd8dec69 UM |
7 | reciprocal |
8 | ||
9 | =head1 SYNOPSIS | |
10 | ||
11 | #include <openssl/bn.h> | |
12 | ||
13 | BN_RECP_CTX *BN_RECP_CTX_new(void); | |
dd8dec69 UM |
14 | void BN_RECP_CTX_free(BN_RECP_CTX *recp); |
15 | ||
16 | int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *m, BN_CTX *ctx); | |
17 | ||
cae55bfc | 18 | int BN_div_recp(BIGNUM *dv, BIGNUM *rem, BIGNUM *a, BN_RECP_CTX *recp, |
e9b77246 | 19 | BN_CTX *ctx); |
cae55bfc | 20 | |
dd8dec69 | 21 | int BN_mod_mul_reciprocal(BIGNUM *r, BIGNUM *a, BIGNUM *b, |
e9b77246 | 22 | BN_RECP_CTX *recp, BN_CTX *ctx); |
dd8dec69 UM |
23 | |
24 | =head1 DESCRIPTION | |
25 | ||
26 | BN_mod_mul_reciprocal() can be used to perform an efficient | |
9b86974e | 27 | L<BN_mod_mul(3)> operation when the operation will be performed |
dd8dec69 UM |
28 | repeatedly with the same modulus. It computes B<r>=(B<a>*B<b>)%B<m> |
29 | using B<recp>=1/B<m>, which is set as described below. B<ctx> is a | |
30 | previously allocated B<BN_CTX> used for temporary variables. | |
31 | ||
32 | BN_RECP_CTX_new() allocates and initializes a B<BN_RECP> structure. | |
dd8dec69 UM |
33 | |
34 | BN_RECP_CTX_free() frees the components of the B<BN_RECP>, and, if it | |
35 | was created by BN_RECP_CTX_new(), also the structure itself. | |
23a1d5e9 | 36 | If B<recp> is NULL, nothing is done. |
dd8dec69 | 37 | |
cae55bfc UM |
38 | BN_RECP_CTX_set() stores B<m> in B<recp> and sets it up for computing |
39 | 1/B<m> and shifting it left by BN_num_bits(B<m>)+1 to make it an | |
40 | integer. The result and the number of bits it was shifted left will | |
41 | later be stored in B<recp>. | |
42 | ||
43 | BN_div_recp() divides B<a> by B<m> using B<recp>. It places the quotient | |
44 | in B<dv> and the remainder in B<rem>. | |
dd8dec69 | 45 | |
e35af275 | 46 | The B<BN_RECP_CTX> structure cannot be shared between threads. |
dd8dec69 UM |
47 | |
48 | =head1 RETURN VALUES | |
49 | ||
50 | BN_RECP_CTX_new() returns the newly allocated B<BN_RECP_CTX>, and NULL | |
51 | on error. | |
52 | ||
c952780c | 53 | BN_RECP_CTX_free() has no return value. |
dd8dec69 UM |
54 | |
55 | For the other functions, 1 is returned for success, 0 on error. | |
9b86974e | 56 | The error codes can be obtained by L<ERR_get_error(3)>. |
dd8dec69 UM |
57 | |
58 | =head1 SEE ALSO | |
59 | ||
9e183d22 | 60 | L<ERR_get_error(3)>, L<BN_add(3)>, |
9b86974e | 61 | L<BN_CTX_new(3)> |
dd8dec69 UM |
62 | |
63 | =head1 HISTORY | |
64 | ||
c952780c | 65 | BN_RECP_CTX_init() was removed in OpenSSL 1.1.0 |
dd8dec69 | 66 | |
e2f92610 RS |
67 | =head1 COPYRIGHT |
68 | ||
9e183d22 | 69 | Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 RS |
70 | |
71 | Licensed under the OpenSSL license (the "License"). You may not use | |
72 | this file except in compliance with the License. You can obtain a copy | |
73 | in the file LICENSE in the source distribution or at | |
74 | L<https://www.openssl.org/source/license.html>. | |
75 | ||
76 | =cut |