Paper 2015/576

The Carnac protocol -- or how to read the contents of a sealed envelope

Michael Scott and Brian Spector

Abstract

Johnny Carson as long time host of the Tonight show often appeared in the spoof role of Carnac the Magnificent, a mentalist who could magically read the contents of a sealed envelope. This is in fact a well known stock-in-trade trick of the mentalist's craft, known as ``billet reading''. Here we propose a cryptographic solution to the problem of billet reading, apparently allowing a cipher-text to be decrypted without direct knowledge of the cipher-text, and present both a compelling use case and a practical implementation.