=pod

=head1 NAME

BN_BLINDING_new, BN_BLINDING_free, BN_BLINDING_update, BN_BLINDING_convert,
BN_BLINDING_invert, BN_BLINDING_convert_ex, BN_BLINDING_invert_ex,
BN_BLINDING_is_current_thread, BN_BLINDING_set_current_thread,
BN_BLINDING_lock, BN_BLINDING_unlock, BN_BLINDING_get_flags,
BN_BLINDING_set_flags, BN_BLINDING_create_param - blinding related BIGNUM functions

=head1 SYNOPSIS

 #include <openssl/bn.h>

 BN_BLINDING *BN_BLINDING_new(const BIGNUM *A, const BIGNUM *Ai,
        BIGNUM *mod);
 void BN_BLINDING_free(BN_BLINDING *b);
 int BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx);
 int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx);
 int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx);
 int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b,
        BN_CTX *ctx);
 int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
        BN_CTX *ctx);
 int BN_BLINDING_is_current_thread(BN_BLINDING *b);
 void BN_BLINDING_set_current_thread(BN_BLINDING *b);
 int BN_BLINDING_lock(BN_BLINDING *b);
 int BN_BLINDING_unlock(BN_BLINDING *b);
 unsigned long BN_BLINDING_get_flags(const BN_BLINDING *);
 void BN_BLINDING_set_flags(BN_BLINDING *, unsigned long);
 BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
        const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
        int (*bn_mod_exp)(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
                          const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx),
        BN_MONT_CTX *m_ctx);

=head1 DESCRIPTION

BN_BLINDING_new() allocates a new B<BN_BLINDING> structure and copies
the B<A> and B<Ai> values into the newly created B<BN_BLINDING> object.

BN_BLINDING_free() frees the B<BN_BLINDING> structure.
If B<b> is NULL, nothing is done.

BN_BLINDING_update() updates the B<BN_BLINDING> parameters by squaring
the B<A> and B<Ai> or, after specific number of uses and if the
necessary parameters are set, by re-creating the blinding parameters.

BN_BLINDING_convert_ex() multiplies B<n> with the blinding factor B<A>.
If B<r> is not NULL a copy the inverse blinding factor B<Ai> will be
returned in B<r> (this is useful if a B<RSA> object is shared among
several threads). BN_BLINDING_invert_ex() multiplies B<n> with the
inverse blinding factor B<Ai>. If B<r> is not NULL it will be used as
the inverse blinding.

BN_BLINDING_convert() and BN_BLINDING_invert() are wrapper
functions for BN_BLINDING_convert_ex() and BN_BLINDING_invert_ex()
with B<r> set to NULL.

BN_BLINDING_is_current_thread() returns whether the B<BN_BLINDING>
structure is owned by the current thread. This is to help users
provide proper locking if needed for multi-threaded use.

BN_BLINDING_set_current_thread() sets the current thread as the
owner of the B<BN_BLINDING> structure.

BN_BLINDING_lock() locks the B<BN_BLINDING> structure.

BN_BLINDING_unlock() unlocks the B<BN_BLINDING> structure.

BN_BLINDING_get_flags() returns the BN_BLINDING flags. Currently
there are two supported flags: B<BN_BLINDING_NO_UPDATE> and
B<BN_BLINDING_NO_RECREATE>. B<BN_BLINDING_NO_UPDATE> inhibits the
automatic update of the B<BN_BLINDING> parameters after each use
and B<BN_BLINDING_NO_RECREATE> inhibits the automatic re-creation
of the B<BN_BLINDING> parameters after a fixed number of uses (currently
32). In newly allocated B<BN_BLINDING> objects no flags are set.
BN_BLINDING_set_flags() sets the B<BN_BLINDING> parameters flags.

BN_BLINDING_create_param() creates new B<BN_BLINDING> parameters
using the exponent B<e> and the modulus B<m>. B<bn_mod_exp> and
B<m_ctx> can be used to pass special functions for exponentiation
(normally BN_mod_exp_mont() and B<BN_MONT_CTX>).

=head1 RETURN VALUES

BN_BLINDING_new() returns the newly allocated B<BN_BLINDING> structure
or NULL in case of an error.

BN_BLINDING_update(), BN_BLINDING_convert(), BN_BLINDING_invert(),
BN_BLINDING_convert_ex() and BN_BLINDING_invert_ex() return 1 on
success and 0 if an error occurred.

BN_BLINDING_is_current_thread() returns 1 if the current thread owns
the B<BN_BLINDING> object, 0 otherwise.

BN_BLINDING_set_current_thread() doesn't return anything.

BN_BLINDING_lock(), BN_BLINDING_unlock() return 1 if the operation
succeeded or 0 on error.

BN_BLINDING_get_flags() returns the currently set B<BN_BLINDING> flags
(a B<unsigned long> value).

BN_BLINDING_create_param() returns the newly created B<BN_BLINDING>
parameters or NULL on error.

=head1 HISTORY

BN_BLINDING_thread_id() was first introduced in OpenSSL 1.0.0, and it
deprecates BN_BLINDING_set_thread_id() and BN_BLINDING_get_thread_id().

=head1 COPYRIGHT

Copyright 2005-2017 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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>.

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