Send message into a Definite Future

Rivest et al proposed a time-lock puzzle scheme for encrypting messages which can only be decrypted in the future. Such a puzzle specifies an algorithm for decrypting the message locked in and the specified algorithm has a well understood time complexity. However, that time-lock puzzle scheme does not provide a means for one to examine whether a puzzle has been formed in good order. Consequently, one may foolishly waste a lengthy time on trying to solve an intractable problem. This weakness prohibits that scheme from applications that involve mutually untrusted parties. We propose a new time-lock puzzle scheme which includes an efficient protocol that allows examination of the time needed for decrypting the message locked in