System Overview

Exploring Our Smart Contract Ecosystem

Our smart contract ecosystem serves 5 primary purposes:

• Enable trading of Pledge Coin (PLG), the main unit of exchange on Pledgecamp
• Enforce holding of, and voting on, backer insurance for projects
• Implement decentralized moderation of projects that have been flagged for review
• Allow staking of PLG in the form of Camp Shares
• Simplify access to the Pledgecamp features with an on-chain managed account system

Pledge Coin is a custom ERC20 implementation with trade locking and token burning capabilities. It was developed and audited in 2018 along with a basic crowdsale contract, located here. Pledge Coin was initially released in February 2019 with a total supply of 1 trillion, and reissued in May 2019 with a total supply of 10 billion. The PLGToken.sol contract in this repository is an exact copy of the version used in the reissue. More details on the contract itself can be found below.

Contract Overview

PLGToken

An ERC20 token with ticker symbol “PLG” used to back projects. This token is an exact copy of the version used in the public crowdsale and the future platform.

PLGProject

A Pledgecamp project starts out as a listing on pledgecamp.com, where backers can contribute funds to receive future rewards. If a project’s funding goal is met within the designated time period, a percentage of the money is automatically paid out to the creator. The remainder of funds are converted to Pledgecamp and sent to a new instance of the PLGProject contract. The amount initially withheld depends on a variable “listing fee,” determined by the creator before publishing the project. Below is an example of what the fee structure could look like:

These numbers are subject to change at any time. The listing fee is dispersed among Camp Share holders (moderators), which you can read more about below.

The PLGProject contract tracks project milestones and backer insurance votes. The creator may withdraw additional funds when a milestone date is passed, as long as the weighted sum of insurance votes does not exceed 50%. If the votes do exceed 50%, backers who voted to receive refunds can withdraw a part of their original investment proportional to the amount of funds still withheld in the contract. The rest of the tokens are available to the creator, so they can attempt to complete the project with less money and fewer obligations to backers.

The contract is initialized with the following project information:

Once the contract is created, its setBackers function is called by the account manager to record project backers, the percentage of each backer's contribution held as insurance, and the total funds received by the project.

After all backers have been recorded in the contract, they may vote to refund at any time by calling milestoneVote. Each vote is weighted by the amount of funds contributed by the backer. When each milestone time is reached (determined by milestoneTimes during initialization), checkMilestones must be called in order to calculate whether refund votes exceed 50%. If they do, the project state is marked as MilestoneFailed, backers who voted to cancel may receive their refund by calling requestRefund, and the creator receives the remaining tokens by calling withdrawFunds. If refund votes are less than 50%, the creator receives a portion of backer insurance according to the milestone's release percentage (provided by releasePercents during initialization).

CampShare

This contract allows participating users to stake PLG, and receive Camp Shares in return at a 1:1 ratio. The contract periodically awards stakers dividends in the form of a percentage of the Pledge Coins collected from project listing fees. The period will tentatively be set to three months, but is subject to change at any time. CS may be converted back to PLG at any time, but dividends will not be awarded for the current period, and the conversion is not finalized until the end of the period. As with all other public facing contract functionality, all Camp Share actions can be done through the managed account system.

A user can convert PLG to CS by using the standard ERC20 function approve to allow a transfer to the CampShare contract. The user then calls the CampShare function acceptPLG, which records the transfer and notes that the user should receive CS at the start of the next dividend period. During this time, the user may call refundPLG to immediately have their PLG returned without waiting until the end of the period.

At the end each period, receiveDividends must be called by each CS holder. It is taken care of automatically if CS was purchased via the managed account system. This triggers a dividend payment if the user has held CS for at least one full dividend period.

Here is a partial example of how the receiveDividends function is implemented. In the code, preCS store intended CS conversions (set when acceptPLG is called), campShares store active CS, and dividendReceiveTimes store the last time of dividend retrieval for each user.

require(dividendReceiveTimes[user] < currentPeriodStart, "Dividends may only be collected once per period");
uint256 shares = campShares[user];
uint256 preCS = preCS[user];
// Transfer dividend
uint256 dividend;
if(shares > 0) {
    dividend = shares.mul(dividendPool).div(totalCS);
    administrator.sendInterest(backer, dividend);
}
// Add CS converted during the last period
campShares[backer] = shares.add(preCS);
totalCS = totalCS.add(preCS);
preCS[backer] = 0;
dividendReceiveTimes[backer] = now;
emit Dividend(user, dividend);

To convert CS back to PLG, the user must first call unstakeCS. At the end of the current dividend period, withdrawPLG can be called to finish the conversion.

In order to receive these dividends, Camp Share stakers have an obligation to moderate projects. At any point in time, the platform backend may request a moderation event due to user reported TOS violations. The Camp Share contracts selects seven moderators in order of when they originally staked PLG. The moderators must vote whether or not to de-list a project within a fixed period of time. If they miss two votes (TBD) in one period, they forfeit dividends for that period.

Account Management

The account management system is split into two contracts. AccountStorage.sol is a mapping of user IDs to token values. It only functions to track user account balances, and enable internal and external token transfers. These transfer functions can only accessed by the contract defined in AccountManager.sol. The account manager contains functions that execute platform operations on behalf of users, including backer insurance voting, Camp Share staking, and project moderation. Pledge Coins are transferred to or from account storage if necessary for the operation (e.g. receiving backer insurance refunds, or converting PLG to CS). Access to the account manager is controlled by the Pledgecamp backend server, which allows authorized users to interact with the platform contracts via pledgecamp.com.

Since the PLGProject contract may be upgraded at any point, separating the token storage from the platform actions is necessary. The storage interface is very simple, so the upgrade process can be done in just a few steps:

• Develop and audit new PLGProject contract
• Upgrade AccountManager.sol to match new project functionality
• Publish the contracts
• Register the new manager contract with the existing storage contract

Administrator

This contract provides various administrative functions necessary for platform operation that don’t fit with the other contracts. It maintains a mapping of project contract addresses to listing fees, which allows creators to set up projects with private wallets, instead of the Pledgecamp account management system. This way the backer insurance rules and listing fees are still enforced, which is a requirement for being listed on pledgecamp.com.

The administrator receives listing fees after projects complete successfully, which are distributed to Camp Share holders periodically. This is handled by the sendDividends function, which is a wrapper around ERC20 token transfer restricted to only allow access to the Camp Share contract.

Finally, the administrator also allows the Camp Share contract to assign project moderators. It maintains a mapping of moderator addresses for every project that allows the Camp Share contract to quickly determine whether a specific Ethereum address is a moderator. The Camp Share contract may set or clear moderator status through administrator functions.

Have a project you want to list? Contact us at hello@pledgecamp.com. For news and updates on when you can begin backing live projects, follow us on one of several options below.

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For more details about the Pledgecamp platform, refer to our white paper accessible at https://pledgecamp.com/whitepaper.

This post may contain forward-looking statements about the future functionality of the platform. The platform is currently in development, and we reserve the right to make changes to the design, names, or functionality of features in the interests of making the platform successful. For full risk factors, see white paper.