Cryptography - Science or Magic?

Examples of the "tricks" that can be performed with modern cryptographic techniques will be presented and each trick explored to see whether it is "science" (i.e., it can be proved to do what it seems to do) or "magic" (i.e., what it seems to do is, or may be, only an illusion). The tricks considered will include no-break cryptography, no-leak secret sharing, no-key cryptography, no-see signatures, no-watch coin tossing, and no-knowledge proofs.