cryptography

Readers are challenged to decipher secret messages, coded diary entries, cryptic inscriptions, and mysterious symbols in an attempt to locate a hoarde of lost treasure from the ancient civilization of the Bilongi Islands.

Presents a guide to codemaking, codebreaking, and their role in history, describing different types of codes and ciphers, discussing codebreaking and concealment techniques, and including brief stories about exciting moments in the history of the art.

Amy and Dan, following a clue found in Book 3, set out to uncover details about the origins of the rivalry between the Tomas and Ekaterina branches of their family, not realizing they are headed right into the hands of the enemy.

Amy and Dan Cahill are in the lead to find thirty-nine clues that safeguard a great power, and are in possession of a coded sheet of Mozart's music that will help them find the next clue while their relatives follow in close pursuit. Includes cards.

Amy and Dan, members of the powerful Cahill family, try to uncover the thirty-nine clues which will reveal the secrets of their lineage and find out what really happened to their parents.

Orphans Amy and Dan Cahill, continuing their worldwide quest to track down the thirty-nine clues that will reveal the secret of the Cahill family's power, follow a link to one of the planet's strongest fighters, and have a run-in with the unreliable Alistair.