.\" $OpenBSD: DSA_generate_parameters.3,v 1.5 2016/12/10 22:47:49 schwarze Exp $ .\" OpenSSL 9b86974e Aug 7 22:14:47 2015 -0400 .\" .\" This file was written by Ulf Moeller , .\" Bodo Moeller , and Matt Caswell . .\" Copyright (c) 2000, 2013 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: December 10 2016 $ .Dt DSA_GENERATE_PARAMETERS 3 .Os .Sh NAME .Nm DSA_generate_parameters_ex , .Nm DSA_generate_parameters .Nd generate DSA parameters .Sh SYNOPSIS .In openssl/dsa.h .Ft int .Fo DSA_generate_parameters_ex .Fa "DSA *dsa" .Fa "int bits" .Fa "const unsigned char *seed" .Fa "int seed_len" .Fa "int *counter_ret" .Fa "unsigned long *h_ret" .Fa "BN_GENCB *cb" .Fc .Pp Deprecated: .Pp .Ft DSA * .Fo DSA_generate_parameters .Fa "int bits" .Fa "unsigned char *seed" .Fa "int seed_len" .Fa "int *counter_ret" .Fa "unsigned long *h_ret" .Fa "void (*callback)(int, int, void *)" .Fa "void *cb_arg" .Fc .Sh DESCRIPTION .Fn DSA_generate_parameters_ex generates primes p and q and a generator g for use in the DSA and stores the result in .Fa dsa . .Pp .Fa bits is the length of the prime to be generated; the DSS allows a maximum of 1024 bits. .Pp If .Fa seed is .Dv NULL or .Fa seed_len < 20, the primes will be generated at random. Otherwise, the seed is used to generate them. If the given seed does not yield a prime q, a new random seed is chosen and placed at .Fa seed . .Pp .Fn DSA_generate_parameters_ex places the iteration count in .Pf * Fa counter_ret and a counter used for finding a generator in .Pf * Fa h_ret , unless these are .Dv NULL . .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 shown below. For information on the .Vt BN_GENCB structure, refer to .Xr BN_GENCB_call 3 . .Bl -bullet .It When a candidate for q is generated, .Fn BN_GENCB_call cb 0 m++ is called .Pf ( Fa m is 0 for the first candidate). .It When a candidate for q has passed a test by trial division, .Fn BN_GENCB_call cb 1 -1 is called. While a candidate for q is tested by Miller-Rabin primality tests, .Fn BN_GENCB_call cb 1 i is called in the outer loop (once for each witness that confirms that the candidate may be prime); .Fa i is the loop counter (starting at 0). .It When a prime q has been found, .Fn BN_GENCB_call cb 2 0 and .Fn BN_GENCB_call cb 3 0 are called. .It Before a candidate for p (other than the first) is generated and tested, .Fn BN_GENCB_call cb 0 counter is called. .It When a candidate for p has passed the test by trial division, .Fn BN_GENCB_call cb 1 -1 is called. While it is tested by the Miller-Rabin primality test, .Fn BN_GENCB_call cb 1 i is called in the outer loop (once for each witness that confirms that the candidate may be prime). .Fa i is the loop counter (starting at 0). .It When p has been found, .Fn BN_GENCB_call cb 2 1 is called. .It When the generator has been found, .Fn BN_GENCB_call cb 3 1 is called. .El .Pp .Fn DSA_generate_parameters (deprecated) works in much the same way as for .Fn DSA_generate_parameters_ex , except that no .Fa dsa parameter is passed and instead a newly allocated .Vt DSA structure is returned. Additionally "old style" callbacks are used instead of the newer .Vt BN_GENCB based approach. Refer to .Xr BN_generate_prime 3 for further information. .Sh RETURN VALUES .Fn DSA_generate_parameters_ex returns a 1 on success, or 0 otherwise. .Pp .Fn DSA_generate_parameters returns a pointer to the .Vt DSA 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 BN_generate_prime 3 , .Xr DSA_new 3 , .Xr ERR_get_error 3 , .Xr RAND_bytes 3 .Sh HISTORY .Fn DSA_generate_parameters appeared in SSLeay 0.8. The .Fa cb_arg argument was added in SSLeay 0.9.0. In versions up to OpenSSL 0.9.4, .Fn callback 1 ...\& was called in the inner loop of the Miller-Rabin test whenever it reached the squaring step (the parameters to .Fn callback did not reveal how many witnesses had been tested); since OpenSSL 0.9.5, .Fn callback 1 ...\& is called as in .Xr BN_is_prime 3 , i.e. once for each witness. .Sh BUGS Seed lengths > 20 are not supported.