digital signature – Understanding public key cryptography example

Frankly, I wasn’t sure whether this belongs in or here, so forgive me. I’ve been going through a book where in one of the chapters the author tries to illustrate public key cryptography by imagining a “four-step business plan for Murder Incorporated” in a “world of strong privacy”.

  1. Arrange for mystery billboards on major highways. Each contains a
    single long number and the message “write this down.” Display ads with
    the same message appear in major newspapers.

  2. Put a full-page ad in the New York Times, apparently written in

  3. Arrange a multiple assassination with high-profile targets, such as
    film stars or major sports figures – perhaps a bomb at the Academy

  4. Send a message to all major media outlets telling them that the number
    on all of those bulletin boards is a public key. If they use it to
    decrypt the New York Times ad they will get a description of the
    assassination, published the day before it happened.

Is the author talking about digital signatures here? The New York Times ad being signed by a private key and the signature is then verified by a corresponding public key found on a billboard?