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

=pod | |

=head1 NAME | |

BN_mod_mul_montgomery, BN_MONT_CTX_new, | |

BN_MONT_CTX_free, BN_MONT_CTX_set, BN_MONT_CTX_copy, | |

BN_from_montgomery, BN_to_montgomery - Montgomery multiplication | |

=head1 SYNOPSIS | |

#include <openssl/bn.h> | |

BN_MONT_CTX *BN_MONT_CTX_new(void); | |

void BN_MONT_CTX_free(BN_MONT_CTX *mont); | |

int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *m, BN_CTX *ctx); | |

BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from); | |

int BN_mod_mul_montgomery(BIGNUM *r, BIGNUM *a, BIGNUM *b, | |

BN_MONT_CTX *mont, BN_CTX *ctx); | |

int BN_from_montgomery(BIGNUM *r, BIGNUM *a, BN_MONT_CTX *mont, | |

BN_CTX *ctx); | |

int BN_to_montgomery(BIGNUM *r, BIGNUM *a, BN_MONT_CTX *mont, | |

BN_CTX *ctx); | |

=head1 DESCRIPTION | |

These functions implement Montgomery multiplication. They are used | |

automatically when L<BN_mod_exp(3)> is called with suitable input, | |

but they may be useful when several operations are to be performed | |

using the same modulus. | |

BN_MONT_CTX_new() allocates and initializes a B<BN_MONT_CTX> structure. | |

BN_MONT_CTX_set() sets up the I<mont> structure from the modulus I<m> | |

by precomputing its inverse and a value R. | |

BN_MONT_CTX_copy() copies the B<BN_MONT_CTX> I<from> to I<to>. | |

BN_MONT_CTX_free() frees the components of the B<BN_MONT_CTX>, and, if | |

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

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

BN_mod_mul_montgomery() computes Mont(I<a>,I<b>):=I<a>*I<b>*R^-1 and places | |

the result in I<r>. | |

BN_from_montgomery() performs the Montgomery reduction I<r> = I<a>*R^-1. | |

BN_to_montgomery() computes Mont(I<a>,R^2), i.e. I<a>*R. | |

Note that I<a> must be nonnegative and smaller than the modulus. | |

For all functions, I<ctx> is a previously allocated B<BN_CTX> used for | |

temporary variables. | |

=head1 RETURN VALUES | |

BN_MONT_CTX_new() returns the newly allocated B<BN_MONT_CTX>, and NULL | |

on error. | |

BN_MONT_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 WARNINGS | |

The inputs must be reduced modulo B<m>, otherwise the result will be | |

outside the expected range. | |

=head1 SEE ALSO | |

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

L<BN_CTX_new(3)> | |

=head1 HISTORY | |

BN_MONT_CTX_init() was removed in OpenSSL 1.1.0 | |

=head1 COPYRIGHT | |

Copyright 2000-2020 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 |