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DH_generate_parameters(3) OpenSSL 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);
DESCRIPTION
DH_generate_parameters_ex() generates Diffie-Hellman parameters that can be shared among a
group of users, and stores them in the provided DH structure. The pseudo-random number
generator must be seeded prior to calling DH_generate_parameters().
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 VALUES
DH_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).
NOTES
DH_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 ALSO
dh(3), ERR_get_error(3), rand(3), DH_free(3)
HISTORY
DH_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.
1.0.2k 2017-01-26 DH_generate_parameters(3)
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On Apache
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