Generate DH key with bigger key

Author: anakinj

test/openssl/test_pkey.rb

@@ -421,7 +421,7 @@ def test_s_from_parameters_dsa_with_invalid_parameter
     end
 
     def test_s_from_parameters_dh_with_all_supported_parameters
-      source  = OpenSSL::PKey::DH.generate(512)
+      source  = OpenSSL::PKey::DH.generate(2048)
 
       new_key =  OpenSSL::PKey.from_parameters("DH", source.params)