1BN_MOD_MUL_RECIPROCAL(3) OpenSSL BN_MOD_MUL_RECIPROCAL(3)
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6 BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, BN_RECP_CTX_free,
7 BN_RECP_CTX_set - modular multiplication using reciprocal
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10 #include <openssl/bn.h>
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12 BN_RECP_CTX *BN_RECP_CTX_new(void);
13 void BN_RECP_CTX_free(BN_RECP_CTX *recp);
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15 int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *m, BN_CTX *ctx);
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17 int BN_div_recp(BIGNUM *dv, BIGNUM *rem, BIGNUM *a, BN_RECP_CTX *recp,
18 BN_CTX *ctx);
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20 int BN_mod_mul_reciprocal(BIGNUM *r, BIGNUM *a, BIGNUM *b,
21 BN_RECP_CTX *recp, BN_CTX *ctx);
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24 BN_mod_mul_reciprocal() can be used to perform an efficient
25 BN_mod_mul(3) operation when the operation will be performed repeatedly
26 with the same modulus. It computes r=(a*b)%m using recp=1/m, which is
27 set as described below. ctx is a previously allocated BN_CTX used for
28 temporary variables.
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30 BN_RECP_CTX_new() allocates and initializes a BN_RECP structure.
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32 BN_RECP_CTX_free() frees the components of the BN_RECP, and, if it was
33 created by BN_RECP_CTX_new(), also the structure itself. If recp is
34 NULL, nothing is done.
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36 BN_RECP_CTX_set() stores m in recp and sets it up for computing 1/m and
37 shifting it left by BN_num_bits(m)+1 to make it an integer. The result
38 and the number of bits it was shifted left will later be stored in
39 recp.
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41 BN_div_recp() divides a by m using recp. It places the quotient in dv
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44 The BN_RECP_CTX structure cannot be shared between threads.
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47 BN_RECP_CTX_new() returns the newly allocated BN_RECP_CTX, and NULL on
48 error.
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50 BN_RECP_CTX_free() has no return value.
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52 For the other functions, 1 is returned for success, 0 on error. The
53 error codes can be obtained by ERR_get_error(3).
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56 ERR_get_error(3), BN_add(3), BN_CTX_new(3)
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59 BN_RECP_CTX_init() was removed in OpenSSL 1.1.0
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62 Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
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64 Licensed under the OpenSSL license (the "License"). You may not use
65 this file except in compliance with the License. You can obtain a copy
66 in the file LICENSE in the source distribution or at
67 <https://www.openssl.org/source/license.html>.
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711.1.1c 2019-05-28 BN_MOD_MUL_RECIPROCAL(3)