# Time locked cryptography using Bitcoin difficulty param and/or smart contract?

Outcome: Create a message with a count down timer. Once a top level password is entered, a countdown timer starts. Once timer expires, the message is decrypted.

Known methods: Proof of work. User has to use computing power to decrypt the message.

Problem: The computer power will change in the future. I want relatively accurate time lock, now & years from now.

Are these possible solutions…?

Proof of work time lock tied to Bitcoin difficulty: Bitcoin has a reactive difficulty parameter that will reflect current state of processing technology.

Is there anyway to use the Bitcoin difficulty parameter as to make a time locking message with a relatively accurate time lock time, now & in the future?

Smart contract based: A smart contract, that once a first layer password is input, a count down timer starts, based on a time now oracle of some kind. Once expired, the second layer message is decrypted.

A) Are any of these possible?

B) Are there any other existing solutions that would get the desired outcome currently?

**Removing serial hashing burden, but still getting the same benefit: ** When top level password is entered, BTC current block is noted. When BTC block reaches current block + X, 2nd layer message is decrypted.

Possible?

The right solution is to use proofs of sequential work, which demonstrate that the prover has executed T steps of a problem which is conjectured to be impossible to parallelize. Many examples exist, based mainly on the conjectured hardness to parallelize modular squaring (given a random $$r$$ and a modulus $$n$$, compute $$r^{2^T} \bmod n$$, where $$n$$ is an hard-to-factor RSA modulus). Many recent papers have worked on related constructions, e.g. look up "proof of sequential work" or "verifiable delay function".