code: private static DSAKeyValidationParameters.Usage getUsage(int usage)
      {
          if (usage == DSAParameterGenerationParameters.DIGITAL_SIGNATURE_USAGE) {
              return DSAKeyValidationParameters.Usage.DIGITAL_SIGNATURE;
          } else if (usage == DSAParameterGenerationParameters.KEY_ESTABLISHMENT_USAGE) {
              return DSAKeyValidationParameters.Usage.KEY_ESTABLISHMENT;
          }
          return DSAKeyValidationParameters.Usage.ANY;
      }
docs: Convert usage index to key usage.
  
  @param usage usage index.
  @return key usage.