.\" $OpenBSD: DH_generate_parameters.3,v 1.5 2016/11/21 11:43:37 schwarze Exp $ .\" OpenSSL 05ea606a May 20 20:52:46 2016 -0400 .\" .\" This file was written by Ulf Moeller . .\" Copyright (c) 2000, 2016 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: November 21 2016 $ .Dt DH_GENERATE_PARAMETERS 3 .Os .Sh NAME .Nm DH_generate_parameters_ex , .Nm DH_check , .Nm DH_generate_parameters .Nd generate and check Diffie-Hellman parameters .Sh SYNOPSIS .In openssl/dh.h .Ft int .Fo DH_generate_parameters_ex .Fa "DH *dh" .Fa "int prime_len" .Fa "int generator" .Fa "BN_GENCB *cb" .Fc .Ft int .Fo DH_check .Fa "DH *dh" .Fa "int *codes" .Fc .Pp Deprecated: .Pp .Ft DH * .Fo DH_generate_parameters .Fa "int prime_len" .Fa "int generator" .Fa "void (*callback)(int" .Fa int .Fa "void *)" .Fa "void *cb_arg" .Fc .Sh DESCRIPTION .Fn DH_generate_parameters_ex generates Diffie-Hellman parameters that can be shared among a group of users, and stores them in the provided .Vt DH structure. .Pp .Fa prime_len is the length in bits of the safe prime to be generated. .Fa generator is a small number > 1, typically 2 or 5. .Pp A callback function may be used to provide feedback about the progress of the key generation. If .Fa cb is not .Dv NULL , it will be called as described in .Xr BN_generate_prime 3 while a random prime number is generated, and when a prime has been found, .Fn BN_GENCB_call cb 3 0 is called; see .Xr BN_GENCB_call 3 . .Pp .Fn DH_check validates Diffie-Hellman parameters. If no problems are found, .Pf * Ar codes is set to zero. Otherwise, one or more of the following bits are set: .Bl -tag -width Ds .It Dv DH_CHECK_P_NOT_PRIME The parameter .Fa dh->p is not prime. .It Dv DH_CHECK_P_NOT_SAFE_PRIME The parameter .Fa dh->p is not a safe prime. .It Dv DH_UNABLE_TO_CHECK_GENERATOR The generator .Fa dh->g cannot be checked for suitability: it is neither 2 nor 5. .It Dv DH_NOT_SUITABLE_GENERATOR The generator .Fa dh->g is not suitable. .El .Sh RETURN VALUES .Fn DH_generate_parameters_ex and .Fn DH_check return 1 if the check could be performed, or 0 otherwise. .Pp .Fn DH_generate_parameters (deprecated) returns a pointer to the .Vt DH structure, or .Dv NULL if the parameter generation fails. .Pp The error codes can be obtained by .Xr ERR_get_error 3 . .Sh SEE ALSO .Xr dh 3 , .Xr DH_new 3 , .Xr ERR_get_error 3 , .Xr RAND_bytes 3 .Sh HISTORY .Fn DH_check is available in all versions of SSLeay and OpenSSL. The .Fa cb_arg argument to .Fn DH_generate_parameters was added in SSLeay 0.9.0. .Pp In versions before OpenSSL 0.9.5, .Dv DH_CHECK_P_NOT_STRONG_PRIME is used instead of .Dv DH_CHECK_P_NOT_SAFE_PRIME . .Sh CAVEATS .Fn DH_generate_parameters_ex and .Fn DH_generate_parameters may run for several hours before finding a suitable prime. .Pp The parameters generated by .Fn DH_generate_parameters_ex and .Fn DH_generate_parameters are not to be used in signature schemes. .Sh BUGS If .Fa generator is not 2 or 5, .Fa dh->g Ns = Ns Fa generator is not a usable generator.