flutter / third_party / openssl / 4b1b629725970384d6cf4dafe9e83e54859574cd / . / doc / man3 / BN_mod_mul_reciprocal.pod

=pod | |

=head1 NAME | |

BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, | |

BN_RECP_CTX_free, BN_RECP_CTX_set - modular multiplication using | |

reciprocal | |

=head1 SYNOPSIS | |

#include <openssl/bn.h> | |

BN_RECP_CTX *BN_RECP_CTX_new(void); | |

void BN_RECP_CTX_free(BN_RECP_CTX *recp); | |

int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *m, BN_CTX *ctx); | |

int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *a, BN_RECP_CTX *recp, | |

BN_CTX *ctx); | |

int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, | |

BN_RECP_CTX *recp, BN_CTX *ctx); | |

=head1 DESCRIPTION | |

BN_mod_mul_reciprocal() can be used to perform an efficient | |

L<BN_mod_mul(3)> operation when the operation will be performed | |

repeatedly with the same modulus. It computes B<r>=(B<a>*B<b>)%B<m> | |

using B<recp>=1/B<m>, which is set as described below. B<ctx> is a | |

previously allocated B<BN_CTX> used for temporary variables. | |

BN_RECP_CTX_new() allocates and initializes a B<BN_RECP> structure. | |

BN_RECP_CTX_free() frees the components of the B<BN_RECP>, and, if it | |

was created by BN_RECP_CTX_new(), also the structure itself. | |

If B<recp> is NULL, nothing is done. | |

BN_RECP_CTX_set() stores B<m> in B<recp> and sets it up for computing | |

1/B<m> and shifting it left by BN_num_bits(B<m>)+1 to make it an | |

integer. The result and the number of bits it was shifted left will | |

later be stored in B<recp>. | |

BN_div_recp() divides B<a> by B<m> using B<recp>. It places the quotient | |

in B<dv> and the remainder in B<rem>. | |

The B<BN_RECP_CTX> structure cannot be shared between threads. | |

=head1 RETURN VALUES | |

BN_RECP_CTX_new() returns the newly allocated B<BN_RECP_CTX>, and NULL | |

on error. | |

BN_RECP_CTX_free() has no return value. | |

For the other functions, 1 is returned for success, 0 on error. | |

The error codes can be obtained by L<ERR_get_error(3)>. | |

=head1 SEE ALSO | |

L<ERR_get_error(3)>, L<BN_add(3)>, | |

L<BN_CTX_new(3)> | |

=head1 HISTORY | |

BN_RECP_CTX_init() was removed in OpenSSL 1.1.0 | |

=head1 COPYRIGHT | |

Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved. | |

Licensed under the Apache License 2.0 (the "License"). You may not use | |

this file except in compliance with the License. You can obtain a copy | |

in the file LICENSE in the source distribution or at | |

L<https://www.openssl.org/source/license.html>. | |

=cut |