class JWT::Decode

def verify_algo
  raise(JWT::IncorrectAlgorithm, 'An algorithm must be specified') if allowed_algorithms.empty?
  raise(JWT::IncorrectAlgorithm, 'Token is missing alg header') unless algorithm
  raise(JWT::IncorrectAlgorithm, 'Expected a different algorithm') unless options_includes_algo_in_header?
end