خرید کتاب Top Secret: A Handbook of Codes, Ciphers and Secret Writing

 Pssst! Do you know the difference between a code and a cipher? Can you tell a St. Cyr slide from a Cardano grille? Did you know that the discovery of a substitution cipher caused Mary Queen of Scots to lose her head? Don’t look now, but packed into this practical field guide is everything a young person needs to know about the art of concealment – making and breaking codes, mastering cipher systems, and experimenting with secret writing. Offering plenty of hands-on practice sessions, tips for creating a code-making kit, sidebars on secret codes in history, and an amusing pair of spies to illustrate techniques, Paul B. Janeczko’s tantalizing TOP SECRET won’t stay a secret for long.