Smart Contracts for Etherland - ELAND ERC20 Token

Contracts Structure

CLONED SOURCE

• We cloned OpenZeppelin Contracts v3 code for SafeMath, ERC20 and ERC20Burnable logic.

  • SafeMath provides arithmetic functions that throw exceptions when integer overflows occur.
  • ERC20 provides a basic implementation of the ERC20 standard
  • ERC20Burnableprovides a burning function that decrement the balance of the burner and the total supply
  • MintableToken provides the token a mintable ability in order to generate the supply

UPGRADED CLONED SOURCE

• We cloned OpenZeppelin Contracts v3 code for Ownable and added some logic.

  • Ownable keeps track of a contract owner and permits the transfer of ownership by the current owner
    • This part of the logic originally propose a straight method named renounceOwnership.
    • We've enhanced this part of the contract's logic by adding a new layer of security materialized by a new method allowing the current owner to definitively relinquish control of the contract in a safe way.
    • This safe check mechanism has been implemented to absolutely avoid situations where a method is unwantely called which could potentially lock the all ecosystem permanently.
    • To make sure this will never happens, we've defined the standalone release process in 2 steps :
      1. First, the owner calls preRenounceOwnership method to generate, store and retrieve an hexadecimal random key named relinquishmentToken.
      2. In a second time, the owner calls renounceOwnership method with relinquishmentToken to renounce to his ownership and set the standalone state to true.
  • ERC20Capped provides a way to add a cap to the supply of tokens ensuring overflow will never happen
    • Constructor has been replaced by a method called setImmutableCap that is called during contract migration (see Flow section of Etherland.sol definition down below)
    • Internal calls to _beforeTokenTransfer are made to ERC20.sol

INTERNAL SOURCE

• LandRegistry.sol Etherland Decentralized Land Registration Protocol

  • Uses iLANDID.sol interface to get the ability to call the hasAdminRights function of Etherland LANDID Non-Fungible-Token smart-contract at address retrievable with the landidNftAddress getter function.
  • On the Etherland Metaverse, any token holder has the ability to register a new land, to do so, they must exchange ELAND Ethereum or any other Token displayed on the offer of Opensea marketplace.
  • Land Record Rights offers and prices are in ELAND or ETH or other Tokens.
  • Those rights are detailed on our website at https://etherland.io/dashboard/?ua=newitem
  • REGISTER A NEW LAND request the mint of an Etherland LANDID Non-Fungible-Token use-case
    • Making a new record in the Land Registry is doable in a few simple steps :
    1. Select a Record Right among the offers at https://etherland.world/register-a-place/
    2. Fill the form and validate all record steps
    3. Validate purchase: A transaction calling the function registerLand is prompted and must be accepted/successfull
    4. Corresponding Record Right is attributed to the caller and safely stored on-chain
    5. Etherland administrator validates the record and mints the corresponding LANDID NFT which caller becomes the owner
    6. Etherland administrator consumes the corresponding Record Right by calling the function consumeRecordRight giving a tokenId
    7. Operation is successfull : a new unique LANDID NFT has been minted which caller is the owner

• Etherland.sol contract assembling the code for Etherland logic

  GENERAL CHARASTERISTICS:

  1. IDENTIFICATION

     • Name : Etherland
     • Symbol : ELAND
     • Decimals : 18

  2. CAP The maximum amount of ELAND tokens the contract will ever mint

     • 1 000 000 000 (1 Billion) units

  3. TOTAL SUPPLY A total available supply of ELAND (will never be higher than the Maximum Supply)

     • starting at capped value of 1 000 000 000 (1 Billion) units
     • may be lower than the Cap along with the burn operations

  4. CIRCULATING SUPPLY The number of circulating ELAND : = totalSupply - team and advisors - reserve - Etherland wallet - Credit carbon reward

  5. MINTING FINISHED In concern for transaprency, we've made available a getter returning a boolean that must be positive with value "true", indicating that its programmatically impossible to mint more tokens than the cap

  6. BURN

     • Any token holder has the ability to burn its own tokens,
     • Burn operations remove the tokens from the total supply

  7. APPROVE

     • Any token holder has the ability to allow a tiers to spend/burn its own tokens

  8. LAND REGISTRY see LandRegistry definition above

  FLOW UPON CONTRACT CONSTRUCTION:

  • Maximum supply is pre-minted
  • Address of the contract owner is initialized
  • Supply is partionnalized and distributed to 3 different wallets :
    • Team wallet : 10% of the maximum supply is allocated to the team
    • Reserve : 20% of the maximum supply is allocated to the reserve
    • Owner : 70% of the maximum supply is transfered to the contract owner
  • Minting is definitvely closed assuring that no more tokens than the maximum supply will be minted

LOCAL TEST FLOW

after having installed dependencies :

1. install yarn running commant yarn install
2. run command yarn test

DEPLOYMENT FLOW

1. If its not done yet, install truffle globally on your system, run npm install -g truffle in a terminal
2. Create or update the .env file at the root of the project with the following environnement variables :
   • OWNER_LIVE : the public address of the contract owner to use on mainnet
   • OWNER_TEST : the public address of the contract owner to use on testnet (rinkeby only)
   • RESERVE_WALLET : the address to use as the reserve wallet for partionning
   • TEAM_WALLET : the address to use as the team wallet for partionning
   • DEPLOY_ETHERLAND_ERC20 : a boolean to allow the deployment flow, set to true if you allow deployment or false otherwise
   • MNEMONIC : seed words separated with a space
   • INFURA_KEY : goto https://infura.io to get an access key
3. Open a terminal at root and run :
   • for Rinkeby : truffle deploy --network rinkeby
   • for Mainnet : truffle deploy --network live

   if you have the up to date message when deploying, maybe you've already deployed the contract before. In that case, if your contract doesnt deploy, simply add the --reset tag as follow : truffle deploy --network rinkeby --reset

/!\ IMPORTANT /!\

DO NOT FORGET NOT TO SHARE YOUR .env MNEMONIC and INFURA_KEY PUBLICLY

PACKAGES VERSION

If any error occurs due to node or npm version, try to update version to :

• npm : 6.14.8 run npm install -g npm@6.14.8
• node : 14.15.0 run nvm use 14.15.0

contact: info@etherland.world