1.\" $OpenBSD: DH_generate_parameters.3,v 1.6 2016/12/10 22:22:59 schwarze Exp $ 2.\" OpenSSL 05ea606a May 20 20:52:46 2016 -0400 3.\" 4.\" This file was written by Ulf Moeller <ulf@openssl.org>. 5.\" Copyright (c) 2000, 2016 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. 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Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: December 10 2016 $ 52.Dt DH_GENERATE_PARAMETERS 3 53.Os 54.Sh NAME 55.Nm DH_generate_parameters_ex , 56.Nm DH_check , 57.Nm DH_generate_parameters 58.Nd generate and check Diffie-Hellman parameters 59.Sh SYNOPSIS 60.In openssl/dh.h 61.Ft int 62.Fo DH_generate_parameters_ex 63.Fa "DH *dh" 64.Fa "int prime_len" 65.Fa "int generator" 66.Fa "BN_GENCB *cb" 67.Fc 68.Ft int 69.Fo DH_check 70.Fa "DH *dh" 71.Fa "int *codes" 72.Fc 73.Pp 74Deprecated: 75.Pp 76.Ft DH * 77.Fo DH_generate_parameters 78.Fa "int prime_len" 79.Fa "int generator" 80.Fa "void (*callback)(int" 81.Fa int 82.Fa "void *)" 83.Fa "void *cb_arg" 84.Fc 85.Sh DESCRIPTION 86.Fn DH_generate_parameters_ex 87generates Diffie-Hellman parameters that can be shared among a group of 88users, and stores them in the provided 89.Vt DH 90structure. 91.Pp 92.Fa prime_len 93is the length in bits of the safe prime to be generated. 94.Fa generator 95is a small number > 1, typically 2 or 5. 96.Pp 97A callback function may be used to provide feedback about the progress 98of the key generation. 99If 100.Fa cb 101is not 102.Dv NULL , 103it will be called as described in 104.Xr BN_generate_prime 3 105while a random prime number is generated, and when a prime has been 106found, 107.Fn BN_GENCB_call cb 3 0 108is called; see 109.Xr BN_GENCB_call 3 . 110.Pp 111.Fn DH_check 112validates Diffie-Hellman parameters. 113If no problems are found, 114.Pf * Ar codes 115is set to zero. 116Otherwise, one or more of the following bits are set: 117.Bl -tag -width Ds 118.It Dv DH_CHECK_P_NOT_PRIME 119The parameter 120.Fa dh->p 121is not prime. 122.It Dv DH_CHECK_P_NOT_SAFE_PRIME 123The parameter 124.Fa dh->p 125is not a safe prime. 126.It Dv DH_UNABLE_TO_CHECK_GENERATOR 127The generator 128.Fa dh->g 129cannot be checked for suitability: it is neither 2 nor 5. 130.It Dv DH_NOT_SUITABLE_GENERATOR 131The generator 132.Fa dh->g 133is not suitable. 134.El 135.Sh RETURN VALUES 136.Fn DH_generate_parameters_ex 137and 138.Fn DH_check 139return 1 if the check could be performed, or 0 otherwise. 140.Pp 141.Fn DH_generate_parameters 142(deprecated) returns a pointer to the 143.Vt DH 144structure, or 145.Dv NULL 146if the parameter generation fails. 147.Pp 148The error codes can be obtained by 149.Xr ERR_get_error 3 . 150.Sh SEE ALSO 151.Xr DH_new 3 , 152.Xr ERR_get_error 3 , 153.Xr RAND_bytes 3 154.Sh HISTORY 155.Fn DH_check 156is available in all versions of SSLeay and OpenSSL. 157The 158.Fa cb_arg 159argument to 160.Fn DH_generate_parameters 161was added in SSLeay 0.9.0. 162.Pp 163In versions before OpenSSL 0.9.5, 164.Dv DH_CHECK_P_NOT_STRONG_PRIME 165is used instead of 166.Dv DH_CHECK_P_NOT_SAFE_PRIME . 167.Sh CAVEATS 168.Fn DH_generate_parameters_ex 169and 170.Fn DH_generate_parameters 171may run for several hours before finding a suitable prime. 172.Pp 173The parameters generated by 174.Fn DH_generate_parameters_ex 175and 176.Fn DH_generate_parameters 177are not to be used in signature schemes. 178.Sh BUGS 179If 180.Fa generator 181is not 2 or 5, 182.Fa dh->g Ns = Ns Fa generator 183is not a usable generator. 184