document BN_reciprocal(3)

1 files changed, 55 insertions, 10 deletions

diff --git a/src/lib/libcrypto/man/BN_mod_mul_reciprocal.3 b/src/lib/libcrypto/man/BN_mod_mul_reciprocal.3
index 77c2932739..f28ade2a41 100644
--- a/src/lib/libcrypto/man/BN_mod_mul_reciprocal.3
+++ b/src/lib/libcrypto/man/BN_mod_mul_reciprocal.3
@@ -1,7 +1,25 @@
-.\"     $OpenBSD: BN_mod_mul_reciprocal.3,v 1.11 2021/11/30 18:34:35 tb Exp $
-.\"     OpenSSL 6859cf74 Sep 25 13:33:28 2002 +0000
+.\" $OpenBSD: BN_mod_mul_reciprocal.3,v 1.12 2022/11/14 18:28:29 schwarze Exp $
+.\" full merge up to: OpenSSL 6859cf74 Sep 25 13:33:28 2002 +0000
+.\" selective merge up to: OpenSSL e9b77246 Jan 20 19:58:49 2017 +0100
 .\"
-.\" This file was written by Ulf Moeller <ulf@openssl.org>.
+.\" This file is a derived work.
+.\" The changes are covered by the following Copyright and license:
+.\"
+.\" Copyright (c) 2022 Ingo Schwarze <schwarze@openbsd.org>
+.\"
+.\" Permission to use, copy, modify, and distribute this software for any
+.\" purpose with or without fee is hereby granted, provided that the above
+.\" copyright notice and this permission notice appear in all copies.
+.\"
+.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.\"
+.\" The original file was written by Ulf Moeller <ulf@openssl.org>.
 .\" Copyright (c) 2000 The OpenSSL Project.  All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
@@ -48,7 +66,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 .\" OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: November 30 2021 $
+.Dd $Mdocdate: November 14 2022 $
 .Dt BN_MOD_MUL_RECIPROCAL 3
 .Os
 .Sh NAME
@@ -57,7 +75,8 @@
 .Nm BN_RECP_CTX_init ,
 .Nm BN_RECP_CTX_free ,
 .Nm BN_RECP_CTX_set ,
-.Nm BN_div_recp
+.Nm BN_div_recp ,
+.Nm BN_reciprocal
 .Nd modular multiplication using reciprocal
 .Sh SYNOPSIS
 .In openssl/bn.h
@@ -95,6 +114,13 @@
 .Fa "BN_RECP_CTX *recp"
 .Fa "BN_CTX *ctx"
 .Fc
+.Ft int
+.Fo BN_reciprocal
+.Fa "BIGNUM *r"
+.Fa "const BIGNUM *m"
+.Fa "int len"
+.Fa "BN_CTX *ctx"
+.Fc
 .Sh DESCRIPTION
 .Fn BN_mod_mul_reciprocal
 can be used to perform an efficient
@@ -160,6 +186,15 @@ It places the quotient in
 and the remainder in
 .Fa rem .
 .Pp
+.Fn BN_reciprocal
+divides the
+.Fa len Ap th
+power of two by
+.Fa m
+and places the quotient in
+.Fa r ,
+rounding it towards zero to the closest integer.
+.Pp
 The
 .Vt BN_RECP_CTX
 structure is defined as follows:
@@ -182,7 +217,17 @@ or
 .Dv NULL
 on error.
 .Pp
-For the other functions, 1 is returned for success or 0 on error.
+.Fn BN_mod_mul_reciprocal ,
+.Fn BN_RECP_CTX_set ,
+and
+.Fn BN_div_recp
+return 1 for success or 0 on error.
+.Pp
+.Fn BN_reciprocal
+returns
+.Fa len
+for success or \-1 on error.
+.Pp
 The error codes can be obtained by
 .Xr ERR_get_error 3 .
 .Sh SEE ALSO
@@ -191,14 +236,14 @@ The error codes can be obtained by
 .Xr BN_new 3
 .Sh HISTORY
 .Fn BN_mod_mul_reciprocal
-first appeared in SSLeay 0.5.1 and has been available since
+and
+.Fn BN_reciprocal
+first appeared in SSLeay 0.5.1 and have been available since
 .Ox 2.4 .
 .Pp
 .Vt BN_RECP_CTX
 was added in SSLeay 0.9.0.
-Before that, a function
-.Fn BN_reciprocal
-was used instead, and the
+Before that, the
 .Fn BN_mod_mul_reciprocal
 arguments were different.
 .Pp