⚰️💰 Ether Tontine

An old proof-of-concept I dusted off and updated to open source. This is not a true tontine as it does not invest capital nor provide interest; it's more akin to a death lottery where the last player standing receives the sum of all contributions. Players must contribute a fixed amount at a fixed interval defined by the opener of the tontine (contract deployer). If a player misses a payment, the player is considered "dead" and can no longer contribute or be considered as the final beneficiary.

Parameters

There are five options when creating a new tontine:

• dues - uint256 amount in wei each player is required to deposit every interval window to be considered "alive".
• interval - uint256 interval window in seconds a player must contribute within (e.g. 31536000 for an annual required payment). Remember that time on-chain is imprecise and malleable by miners to a degree so a high frequency tontine is for true adrenaline fiends. It might go without saying that an interval shorter than the typical block time won't work.
• minPlayers - uint256 of the required number of players to deposit a first payment for the interval to begin ticking. This allows the game to begin slowly without requiring fast coordination between all players and the tontine will remain in a paused state until the required minimum is met. Once the nth player joins, the game begins and payments at interval are expected.
• allowLatecomers - bool that determines whether players can join after the game clock has started ticking. This allows the potential growth rate of the pot to continue increasing over time but also offers no disadvantage to latecomers.
• heirMustLive - bool that determines whether the final claimant must be in a "living" state, i.e. in good standing with dues payments. Set this to false so that should all players forget about the tontine, the funds can still be withdrawn by the first player to remember to do so. Otherwise the chest is effectively burned.

Lifecycle

1. The deployer of the contract creates a new tontine with the parameters described above. The tontine creator otherwise has no special privileges.
2. Players wishing to join call the contribute() method with the amount of ether defined as the periodic dues.
3. The tontine remains in a paused state until player n joins, where n is defined as minPlayers. At this point, the last payment time of each player is set to the block timestamp of the nth player's entrance transaction.
4. Players must call contribute() with dues within each subsequent interval. Missing a payment causes future ones from that player to be rejected and the player is considered to be expired.
5. Perhaps a century in the future (or a week, depending on how seriously the game is taken) a savvy player will notice that all other players have eventually missed a payment and will call claim(). If indeed all other players are dead, the contract will self destruct, sending its full balance to the final heir.

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caveat emptor: Many smart contracts turn out to be tacitly dumb and this may well be one of them; i.e. use at your own risk.