MySQL:

CREATE_DH_PARAMETERS

create_dh_parameters(key_len)

Creates a shared secret for generating a DH private/public key pair and
returns a binary string that can be passed to
create_asymmetric_priv_key(). If secret generation fails, the result is
null.

Supported key_len values: The minimum and maximum key lengths in bits
are 1,024 and 10,000. These key-length limits are constraints imposed
by OpenSSL. Server administrators can impose additional limits on
maximum key length by setting environment variables.

For an example showing how to use the return value for generating
symmetric keys, see the description of asymmetric_derive().

Example

SET @dhp = create_dh_parameters(1024);