=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_set_thread, BN_BLINDING_cmp_thread, 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);

 void BN_BLINDING_set_thread(BN_BLINDING *);
 int BN_BLINDING_cmp_thread(const BN_BLINDING *,
        const CRYPTO_THREADID *);
 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.

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 amoung
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_set_thread() and BN_BLINDING_cmp_thread()
set and compare the "thread id" of the B<BN_BLINDING> structure,
allowing users of the B<BN_BLINDING> structure to
provide proper locking if needed for multi-threaded use.

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 occured.

BN_BLINDING_get_thread_id() returns the thread id (a B<unsigned long>
value) or 0 if not set.
BN_BLINDING_cmp_thread() returns 0 if the thread id associated with the
B<BN_BLINDING> structure equals the provided thread id (which can be
obtained by CRYPTO_THREADID_set()), otherwise it returns -1 or +1
to indicate the thread ids are different (if the target architecture
supports ordering of thread ids, this follows the traditional "cmp"
semantics of memcmp() or strcmp()).

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 SEE ALSO

L<bn(3)|bn(3)>

=head1 HISTORY

BN_BLINDING_convert_ex, BN_BLINDIND_invert_ex, BN_BLINDING_get_thread_id,
BN_BLINDING_set_thread_id, BN_BLINDING_set_flags, BN_BLINDING_get_flags
and BN_BLINDING_create_param were first introduced in OpenSSL 0.9.8

BN_BLINDING_get_thread_idptr, BN_BLINDING_set_thread_idptr were first
introduced in OpenSSL 0.9.9

BN_BLINDING_get_thread_id, BN_BLINDING_set_thread_id,
BN_BLINDING_get_thread_idptr, BN_BLINDING_set_thread_idptr were all
deprecated in favour of BN_BLINDING_set_thread, BN_BLINDING_cmp_thread
which were introduced in OpenSSL 0.9.9

=head1 AUTHOR

Nils Larsch for the OpenSSL project (http://www.openssl.org).

=cut