MirBSD manpage: DH_check(3), DH_generate_parameters(3)

DH_GENERATE_PARAMETERS(3)    OpenSSL    DH_GENERATE_PARAMETERS(3)

NAME

     DH_generate_parameters, DH_check - generate and check
     Diffie-Hellman parameters

SYNOPSIS

      #include <openssl/dh.h>

      DH *DH_generate_parameters(int prime_len, int generator,
          void (*callback)(int, int, void *), void *cb_arg);

      int DH_check(DH *dh, int *codes);

DESCRIPTION

     DH_generate_parameters() generates Diffie-Hellman parameters
     that can be shared among a group of users, and returns them
     in a newly allocated 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 gen-
     erated. 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 callback 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, callback(3, 0, cb_arg) is called.

     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() returns a pointer to the DH struc-
     ture, or NULL if the parameter generation fails. The error
     codes can be obtained by ERR_get_error(3).

     DH_check() returns 1 if the check could be performed, 0 oth-
     erwise.

NOTES

     DH_generate_parameters() may run for several hours before
     finding a suitable prime.

     The parameters generated by 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

MirBSD #10-current         2005-02-05                           1

DH_GENERATE_PARAMETERS(3)    OpenSSL    DH_GENERATE_PARAMETERS(3)

     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.

MirBSD #10-current         2005-02-05                           2