Issue #701: Update on fidelity bonds

In early August of last year, we made you freaks aware of fidelity bonds, which were proposed on the Bitcoin-Dev mailing list by Chris Belcher. In short, fidelity bonds aim to combat Sybil attacks on CoinJoins by forcing makers in a JoinMarket setup to lock up their UTXOs for x amount of blocks using OP_CHECKLOCKTIMEVERIFY. This would extend the amount of time it takes to successfully pull off the attack while subjecting the attacker to longer-term price risk. Hopefully discouraging them from even attempting the attack in the first place while aligning with long-term incentives of holders. Fidelity bonds would incentivize long-term holders to provide CoinJoin liquidity by thwarting attackers, which provides better privacy assurances, which makes bitcoin more useful, which drives demand, which increases price as individuals fight for a fixed amount of bitcoins.

Pull Request for adding fidelity bond wallets to @joinmarket opened https://t.co/6GVdZRd8af Sybil-resistant privacy is coming. Locked up coins can be used to prove a sacrifice in a way that can't be faked, in a similar way to PoW in mining.
— belcher (@chris_belcher_) March 21, 2020

Well, over the weekend, Chris Belcher officially submitted a pull request in the JoinMarket GitHub repository to have fidelity bond compatible wallets added to the software. Pushing the privacy assurances ball forward by a bit more. This is very encouraging to see. As you freaks know if you've been reading this rag for long enough, bitcoin's current privacy assurances are sub-par. Privacy is an ideal that users and developers strive for and has gotten better over time. Developments like fidelity bonds prove, to me, that progress is being made in this department.

Couple the development of fidelity bonds with the recent massive uptick in volume within Samourai Wallet's Whirpool CoinJoin implementation and it seems like we're hitting an inflection point in terms of quality privacy tools that are coming to market for bitcoiners. Granted, fidelity bonds are nothing but a PR at the moment. However, I imagine their existence will add to the quality of JoinMarket, driving more usage. Aiding in increasing the anonymity set for bitcoiners everywhere. And, now that I recheck the GitHub page, it seems like the PR is ready to be merged.