/usr/man/cat.3/DH_generate_parameters_ex.3

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).

1.0.2t               Last change: 2019-09-10                    1

DH_generate_parameters(3)    OpenSSL    DH_generate_parameters(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.

1.0.2t               Last change: 2019-09-10                    2

See also DH_check(3)
See also DH_generate_parameters(3)