Understanding the wCCD smart contract

The native currency on the Concordium blockchain is CCD. When other tokens are built on the Concordium blockchain, they often use the recommended CIS-2 token standard. This has the advantage that other dApps (decentralized apps) can rely on some basic rules for how to interact with the CIS-2 tokens and on some basic rules for how the apps can retrieve events and data from the CIS-2 tokens. The native currency CCD has a special purpose in the Concordium blockchain network and does not comply with the CIS-2 token standard.

Note

The CIS-2 standard can represent fungible and non-fungible tokens. It combines the Ethereum ERC20 and ERC721 standards with some modifications. The CIS-2 library is meant to be imported by CIS-2 tokens. Please explore the five CIS-2 token standard implementation examples in the Concordium smart contract repo:

• natively-upgradable wccd

• nft

• dynamic-nft

• multi

• multi-royalties

Implementing two interfaces (one for CCD and another for CIS-2 tokens) within the same smart contract can be cumbersome for developers and adds complexity. You need a process that converts CCD into a token (named wCCD) that is CIS-2 compliant so dApps can interact with it easily. For example, decentralized exchanges depend on the wCCD token because the wCCD token can be traded with other CIS-2 tokens.

Wrapping CCD refers to the process of converting the native currency CCD into a CIS-2 compliant token (wCCD) at a 1:1 ratio by sending CCD to the wCCD smart contract and getting wCCD in return. The wrap function accepts an amount of CCD and mints(creates) the same amount of wCCD tokens. It takes a receiving address as the parameter and transfers the minted amount of wCCD tokens to this receiver.

Unwrapping CCD refers to the opposite process of converting the CIS-2 compliant wCCD token at a 1:1 ratio back to the native currency CCD by burning(destroying) the wCCD token in the wCCD smart contract and getting CCD in return. The unwrap function takes the amount of tokens to unwrap and burns(destroys) them before transferring the same amount of CCD to the receiver.

The circulating supply of the wCCD token is backed 1:1 by the CCD balance on the wCCD smart contract.

Contract addresses

The Concordium foundation maintains the canonical wCCD smart contract and promotes its usage to create a coherent overall smart contract ecosystem on the Concordium blockchain. The wCCD smart contract deployed can be upgraded to add additional features and to improve the smart contract based on the newest science and research done at Concordium. The protocol is free of charge and no commissions are collected by Concordium.

Note

The testnet address below is an early version of the wCCD smart contract. Some minor changes can be expected.

The canonical wCCD smart contract following the CIS-2 standard is deployed on testnet at the following addresses:

wCCD (Testnet): <2059,0>

The canonical wCCD smart contract following the CIS-2 standard is deployed on mainnet at the following addresses:

wCCD (Mainnet): <9354,0>

Note

The wCCD smart contract is upgradeable, but the wCCD contract address will always stay the same. Only the module pointer (a reference to the code that is executed) is updated in the smart contract during an upgrade.

You have now read all information necessary to begin interacting with the wCCD smart contract on testnet. To continue with the tutorial click here.