DH_generate_parameters(3) LibreSSL DH_generate_parameters(3)NAME
DH_generate_parameters_ex, DH_generate_parameters, DH_check - generate
and check Diffie-Hellman parameters
SYNOPSIS
#include <openssl/dh.h>
int DH_generate_parameters_ex(DH *dh, int prime_len,int generator, BN_GENCB *cb);
int DH_check(DH *dh, int *codes);
Deprecated:
DH *DH_generate_parameters(int prime_len, int generator,
void (*callback)(int, int, void *), void *cb_arg);
DESCRIPTIONDH_generate_parameters_ex() generates Diffie-Hellman parameters that
can be shared among a group of users, and stores them in the provided
DH structure.
prime_len is the length in bits of the safe prime to be generated.
generator is a small number > 1, typically 2 or 5.
A callback function may be used to provide feedback about the progress
of the key generation. If cb is not NULL, it will be called as
described in BN_generate_prime(3) while a random prime number is
generated, and when a prime has been found, BN_GENCB_call(cb, 3, 0) is
called. See BN_generate_prime(3) for information on the BN_GENCB_call()
function.
DH_check() validates Diffie-Hellman parameters. It checks that p is a
safe prime, and that g is a suitable generator. In the case of an
error, the bit flags DH_CHECK_P_NOT_SAFE_PRIME or
DH_NOT_SUITABLE_GENERATOR are set in *codes.
DH_UNABLE_TO_CHECK_GENERATOR is set if the generator cannot be checked,
i.e. it does not equal 2 or 5.
RETURN VALUESDH_generate_parameters_ex() and DH_check() return 1 if the check could
be performed, 0 otherwise.
DH_generate_parameters() (deprecated) returns a pointer to the DH
structure, or NULL if the parameter generation fails.
The error codes can be obtained by ERR_get_error(3).
NOTESDH_generate_parameters_ex() and DH_generate_parameters() may run for
several hours before finding a suitable prime.
The parameters generated by DH_generate_parameters_ex() and
DH_generate_parameters() are not to be used in signature schemes.
BUGS
If generator is not 2 or 5, dh->g=generator is not a usable generator.
SEE ALSOdh(3), ERR_get_error(3), rand(3), DH_free(3)HISTORYDH_check() is available in all versions of SSLeay and OpenSSL. The
cb_arg argument to DH_generate_parameters() was added in SSLeay 0.9.0.
In versions before OpenSSL 0.9.5, DH_CHECK_P_NOT_STRONG_PRIME is used
instead of DH_CHECK_P_NOT_SAFE_PRIME.
LibreSSL 2015-03-19 DH_generate_parameters(3)
