While you're taking editing suggestions, there are 2 points that are missing in the narrative:

- Alice and Bob must have identical copies of the dictionary. Different editions could have slightly different definitions. The risk is not large, but it throws off all confidence.

- Alice tells Bob her procedure. Either they do it in real-time together or she tells him the procedure along with the encrypted word. But nowhere in the text as written does Alice communicate the "algorithm" to Bob.

Also, Bob does not know if Alice completed the puzzle until he completes the puzzle (or the solution is published) [actually that one clue, but Alice could've chosen any clue, possibly the last one that Bob finds]. The story made me believe Bob would know if Alice completed the puzzle immediately, so by definition of the problem, before he completed it. Is there a protocol that would allow this? [I think that's where we need 3rd party trusted sources]