5 BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, BN_RECP_CTX_init,
6 BN_RECP_CTX_free, BN_RECP_CTX_set - modular multiplication using
11 #include <openssl/bn.h>
13 BN_RECP_CTX *BN_RECP_CTX_new(void);
14 void BN_RECP_CTX_free(BN_RECP_CTX *recp);
16 int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *m, BN_CTX *ctx);
18 int BN_div_recp(BIGNUM *dv, BIGNUM *rem, BIGNUM *a, BN_RECP_CTX *recp,
21 int BN_mod_mul_reciprocal(BIGNUM *r, BIGNUM *a, BIGNUM *b,
22 BN_RECP_CTX *recp, BN_CTX *ctx);
26 BN_mod_mul_reciprocal() can be used to perform an efficient
27 L<BN_mod_mul(3)|BN_mod_mul(3)> operation when the operation will be performed
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.
32 BN_RECP_CTX_new() allocates and initializes a B<BN_RECP> structure.
33 BN_RECP_CTX_init() initializes an existing uninitialized B<BN_RECP>.
35 BN_RECP_CTX_free() frees the components of the B<BN_RECP>, and, if it
36 was created by BN_RECP_CTX_new(), also the structure itself.
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>.
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>.
46 The B<BN_RECP_CTX> structure cannot be shared between threads.
50 BN_RECP_CTX_new() returns the newly allocated B<BN_RECP_CTX>, and NULL
53 BN_RECP_CTX_init() and BN_RECP_CTX_free() have no return values.
55 For the other functions, 1 is returned for success, 0 on error.
56 The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
58 =head1 REMOVED FUNCTIONALITY
60 void BN_RECP_CTX_init(BN_RECP_CTX *recp);
62 BN_RECP_CTX_init() is no longer available as of OpenSSL 1.1.0. It was used to
63 initialize an existing uninitialized B<BN_RECP_CTX>. Typically this would be
67 BN_RECP_CTX_init(&ctx);
69 Applications should replace use of BN_RECP_CTX_init with BN_RECP_CTX_new
73 ctx = BN_RECP_CTX_new();
74 if(!ctx) /* Handle error */
76 BN_RECP_CTX_free(ctx);
80 L<bn(3)|bn(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<BN_add(3)|BN_add(3)>,
81 L<BN_CTX_new(3)|BN_CTX_new(3)>
85 B<BN_RECP_CTX> was added in SSLeay 0.9.0. Before that, the function
86 BN_reciprocal() was used instead, and the BN_mod_mul_reciprocal()
87 arguments were different. BN_RECP_CTX_init was removed in OpenSSL 1.1.0