This is an Erlang implementation of the Fernet specification which
"takes a user-provided message (an arbitrary sequence of bytes), a key (256 bits), and the current time, and produces a token, which contains the message in a form that can't be read or altered without the key."
1> Key = fernet:generate_encoded_key().
<<"iXOktbuC7QYXM9aF_m49VAqdkZ6jQBMsqjYwEHTm5ps=">>
2> Token = fernet:generate_token("hello", Key).
<<"gAAAAABVguk6wOivag6ZN_76fP2EXltZGJ9yPLLXKg4aBR9ekbhVnYmkJOuqTGl_GlmNlg6Z_KDl2wb1duRV41CNbF931n4LgA==">>
3> fernet:verify_and_decrypt_token(Token, Key, infinity).
{ok,<<"hello">>}
4> TTL = 10. % seconds
10
5> fernet:verify_and_decrypt_token(Token, Key, TTL).
{error, too_old}