def return_hash(final_vector)
      case digest_length
      when 512
        create_digest(final_vector)
      when 256
        create_digest(vector_from_array(final_vector[0..31]))
      else
        raise ArgumentError,
              "digest length must be equal to 256 or 512, not #{digest_length}"
      end
    end
def return_hash(final_vector)
      case digest_length
      when 512
        create_digest(final_vector)
      when 256
        create_digest(vector_from_array(final_vector[0..31]))
      else
        raise ArgumentError,
              "digest length must be equal to 256 or 512, not #{digest_length}"
      end
    end
Method, which return digest, dependent on them length