.\"	$OpenBSD: BN_BLINDING_new.3,v 1.12 2023/04/25 20:07:55 tb Exp $
.\"	OpenSSL a528d4f0 Oct 27 13:40:11 2015 -0400
.\"
.\" This file was written by Nils Larsch <nils@openssl.org>.
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.Dd $Mdocdate: April 25 2023 $
.Dt BN_BLINDING_NEW 3
.Os
.Sh NAME
.Nm BN_BLINDING_new ,
.Nm BN_BLINDING_free ,
.Nm BN_BLINDING_update ,
.Nm BN_BLINDING_convert ,
.Nm BN_BLINDING_invert ,
.Nm BN_BLINDING_convert_ex ,
.Nm BN_BLINDING_invert_ex ,
.Nm BN_BLINDING_thread_id ,
.Nm BN_BLINDING_get_flags ,
.Nm BN_BLINDING_set_flags ,
.Nm BN_BLINDING_create_param
.Nd blinding related BIGNUM functions
.Sh SYNOPSIS
.In openssl/bn.h
.Ft BN_BLINDING *
.Fo BN_BLINDING_new
.Fa "const BIGNUM *A"
.Fa "const BIGNUM *Ai"
.Fa "BIGNUM *mod"
.Fc
.Ft void
.Fo BN_BLINDING_free
.Fa "BN_BLINDING *b"
.Fc
.Ft int
.Fo BN_BLINDING_update
.Fa "BN_BLINDING *b"
.Fa "BN_CTX *ctx"
.Fc
.Ft int
.Fo BN_BLINDING_convert
.Fa "BIGNUM *n"
.Fa "BN_BLINDING *b"
.Fa "BN_CTX *ctx"
.Fc
.Ft int
.Fo BN_BLINDING_invert
.Fa "BIGNUM *n"
.Fa "BN_BLINDING *b"
.Fa "BN_CTX *ctx"
.Fc
.Ft int
.Fo BN_BLINDING_convert_ex
.Fa "BIGNUM *n"
.Fa "BIGNUM *r"
.Fa "BN_BLINDING *b"
.Fa "BN_CTX *ctx"
.Fc
.Ft int
.Fo BN_BLINDING_invert_ex
.Fa "BIGNUM *n"
.Fa "const BIGNUM *r"
.Fa "BN_BLINDING *b"
.Fa "BN_CTX *ctx"
.Fc
.Ft CRYPTO_THREADID *
.Fo BN_BLINDING_thread_id
.Fa "BN_BLINDING *"
.Fc
.Ft unsigned long
.Fo BN_BLINDING_get_flags
.Fa "const BN_BLINDING *"
.Fc
.Ft void
.Fo BN_BLINDING_set_flags
.Fa "BN_BLINDING *"
.Fa "unsigned long"
.Fc
.Ft BN_BLINDING *
.Fo BN_BLINDING_create_param
.Fa "BN_BLINDING *b"
.Fa "const BIGNUM *e"
.Fa "BIGNUM *m"
.Fa "BN_CTX *ctx"
.Fa "int (*bn_mod_exp)(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,\
 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)"
.Fa "BN_MONT_CTX *m_ctx"
.Fc
.Sh DESCRIPTION
.Fn BN_BLINDING_new
allocates a new
.Vt BN_BLINDING
structure and copies the
.Fa A
and
.Fa \&Ai
values into the newly created
.Vt BN_BLINDING
object.
.Pp
.Fn BN_BLINDING_free
frees the
.Vt BN_BLINDING
structure.
If
.Fa b
is a
.Dv NULL
pointer, no action occurs.
.Pp
.Fn BN_BLINDING_update
updates the
.Vt BN_BLINDING
parameters by squaring the
.Fa A
and
.Fa \&Ai
or, after a specific number of uses and if the necessary parameters are
set, by re-creating the blinding parameters.
.Pp
.Fn BN_BLINDING_convert_ex
multiplies
.Fa n
with the blinding factor
.Fa A .
If
.Fa r
is not
.Dv NULL ,
a copy of the inverse blinding factor
.Fa \&Ai
will be returned in
.Fa r
(this is useful if an
.Vt RSA
object is shared among several threads).
.Fn BN_BLINDING_invert_ex
multiplies
.Fa n
with the inverse blinding factor
.Fa \&Ai .
If
.Fa r
is not
.Dv NULL ,
it will be used as the inverse blinding.
.Pp
.Fn BN_BLINDING_convert
and
.Fn BN_BLINDING_invert
are wrapper functions for
.Fn BN_BLINDING_convert_ex
and
.Fn BN_BLINDING_invert_ex
with
.Fa r
set to
.Dv NULL .
.Pp
.Fn BN_BLINDING_thread_id
provides access to the
.Vt CRYPTO_THREADID
object within the
.Vt BN_BLINDING
structure.
This is to help users provide proper locking if needed for
multi-threaded use.
The thread ID object of a newly allocated
.Vt BN_BLINDING
structure is initialised to the thread ID in which
.Fn BN_BLINDING_new
was called.
.Pp
.Fn BN_BLINDING_get_flags
returns the
.Dv BN_BLINDING_*
flags.
Currently there are two supported flags:
.Dv BN_BLINDING_NO_UPDATE
and
.Dv BN_BLINDING_NO_RECREATE .
.Dv BN_BLINDING_NO_UPDATE
inhibits the automatic update of the
.Vt BN_BLINDING
parameters after each use and
.Dv BN_BLINDING_NO_RECREATE
inhibits the automatic re-creation of the
.Vt BN_BLINDING
parameters after a fixed number of uses (currently 32).
In newly allocated
.Vt BN_BLINDING
objects no flags are set.
.Fn BN_BLINDING_set_flags
sets the
.Dv BN_BLINDING_*
parameters flags.
.Pp
.Fn BN_BLINDING_create_param
creates new
.Vt BN_BLINDING
parameters using the exponent
.Fa e
and the modulus
.Fa m .
.Fa bn_mod_exp
and
.Fa m_ctx
can be used to pass special functions for exponentiation (normally
.Xr BN_mod_exp 3
and
.Vt BN_MONT_CTX ) .
.Sh RETURN VALUES
.Fn BN_BLINDING_new
returns the newly allocated
.Vt BN_BLINDING
structure or
.Dv NULL
in case of an error.
.Pp
.Fn BN_BLINDING_update ,
.Fn BN_BLINDING_convert ,
.Fn BN_BLINDING_invert ,
.Fn BN_BLINDING_convert_ex
and
.Fn BN_BLINDING_invert_ex
return 1 on success and 0 if an error occurred.
.Pp
.Fn BN_BLINDING_thread_id
returns a pointer to the thread ID object within a
.Vt BN_BLINDING
object.
.Pp
.Fn BN_BLINDING_get_flags
returns the currently set
.Dv BN_BLINDING_*
flags (an
.Vt unsigned long
value).
.Pp
.Fn BN_BLINDING_create_param
returns the newly created
.Vt BN_BLINDING
parameters or
.Dv NULL
on error.
.Sh SEE ALSO
.Xr BN_new 3 ,
.Xr RSA_blinding_on 3
.Sh HISTORY
.Fn BN_BLINDING_new ,
.Fn BN_BLINDING_free ,
.Fn BN_BLINDING_update ,
.Fn BN_BLINDING_convert ,
and
.Fn BN_BLINDING_invert
first appeared in SSLeay 0.9.0 and have been available since
.Ox 2.4 .
.Pp
.Fn BN_BLINDING_convert_ex ,
.Fn BN_BLINDIND_invert_ex ,
.Fn BN_BLINDING_get_flags ,
.Fn BN_BLINDING_set_flags ,
and
.Fn BN_BLINDING_create_param
first appeared in OpenSSL 0.9.8 and have been available since
.Ox 4.5 .
.Pp
.Fn BN_BLINDING_thread_id
first appeared in OpenSSL 1.0.0 and has been available since
.Ox 4.9 .
.Sh AUTHORS
.An Nils Larsch Aq Mt nils@openssl.org