|Alice holds a shard, raises her other hand, and injects the key phrase: “Gallows Goblets Gold.”|
|She then lowers her hand, and thinks her message: “Hello Bob.”|
|Bob, who knows the keyphrase “Gallows Goblets Gold” sees the message: “Hello, Bob.”|
|Chuck, who does not know the keyphrase, sees only jumbled cypher-text|
Luckily, Alice and Bob previously agreed on a shared keyphrase… a string of words that encrypt the clear-text into cipher-text (that is, unintelligible nonsense). The cipher-text can only be decrypted (transformed back into clear-text) by someone who knows this keyphrase. Alice raises her hand to her shard and thinks the keyphrase. She then lowers her hand, and thinks the message “Watch out, Chuck is working for the enemy.” Bob, who knows the keyphrase, receives the message loud and clear. Chuck, however, only receives confusing cipher-text. He now knows that Alice and Bob are keeping a secret from him, but does not know what that secret is.