Sign a payload that expires in ten seconds with JWTs and twisted Edwards curves (Ruby in Hollywood)

jwt.rb

# gem install jwt rbnacl

require 'jwt'
require 'securerandom'

command = 'flee to the hills!'
ten_seconds_from_now = Time.now.to_i + 10

payload = {
  data: command,
  exp: ten_seconds_from_now
}

##
# Encrypt your payload.
signing_key = RbNaCl::Signatures::Ed25519::SigningKey.new SecureRandom.bytes 32
signature = signing_key.to_bytes # Save your signature to sign other things.
password = signing_key.verify_key.to_bytes # Use your password to decrypt.
token = JWT.encode payload, signing_key, 'ED25519' # Share the encrypted payload.

##
# Decrypt your payload.
verify_key = RbNaCl::Signatures::Ed25519::VerifyKey.new password
begin
  decrypted_payload, _ = JWT.decode token, verify_key, true, {algorithm: 'ED25519'}
rescue JWT::ExpiredSignature
  abort 'Too late!'
end

puts decrypted_payload['data']