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Author: Tanuj Surve, Cointelegraph; Compiled by: Deng Tong, Bitchain Vision
Once all specified terms or conditions in the contract or agreement are met, the smart contract hosted on the blockchain is automatically executed without intermediary intervention.
The terms of the contract are written in machine-readable code.Once a smart contract is completed, it is irreversible and legally binding, which raises a question:Can a smart contract be terminated?More importantly, can smart contracts be reversed?
This article discusses whether it is possible to revoke a smart contract and, if possible, how to revoke access to the cryptocurrency it holds.
What does revoking a smart contract mean?
Revoking a smart contract usually means disabling or terminating its functionality on the blockchain.For example, revoking may block access to users’ crypto wallets and mobile tokens.Additionally, revoking the smart contract will stop viewing the user token balance or public address.
Why are smart contracts revoked?
People can withdraw smart contracts in a variety of situations, such as if they do not intend to buy, sell, or transfer assets or use smart contracts again.
In other cases, malicious developers build backdoors in smart contracts, allowing unauthorized access to funds.
Who can change the smart contract?
Like any contract, it cannot be changed once the parties agree on the terms of the contract.Even if both parties are willing to do so, the terms are written on the blockchain and cannot be changed.This makes smart contracts immutable.
The only way to “change” the terms of a contract is to “upgrade” the contract, which is to replace the underlying smart contract for a decentralized application (DApp) with another.Alternatively, both parties can choose to have an upgradeable contract from the beginning, so that they can modify the smart contract.
Who controls smart contracts?
Once the code is written to the blockchain, no one can control the smart contract.If a predetermined condition or provision is met or verified, the code will be executed.This operation involves updating the blockchain and sending notifications.Only parties with access to smart contracts can see transaction details.
Since no one has clear control over the contract, both parties need to determine the terms and fully describe them, and must not be ambiguous to ensure that the contract can be enforced.This raises the question: Can tokens be locked in smart contracts?When a user sends tokens into a smart contract, no one can trade or withdraw them, basically locking them in it.
Smart contracts will only release tokens after a certain period of time or after certain conditions are met.Some platforms even allow custom token locking, where users can specify the date and time of the token available.
What are the token approvals and permissions in smart contracts?
The only way to prevent smart contracts from being exploited is to approve only the withdrawal of required funds, avoid untested platforms, and revoke token approvals and permissions.
But what are token approvals and permissions?Smart contracts allow DApps to automatically move tokens in their wallets, thus obtaining token approval and permission.Therefore, token approval and permissions mean that the owner approves the smart contract to withdraw tokens from the wallet to execute the transaction.There are a number of ways users can revoke access to their tokens by smart contracts.
Revoke smart contracts through token block browser
A single network often has block browsers such as Polygonscan and Etherscan, which contain approval sections where users can revoke permissions and approvals using the token approval tool.
Here are the typical steps taken when using the token approval tool, please note that only the address owner can revoke a connected smart contract:
1. Navigate to the token approval page.
2. Enter your address in the search bar and click Search.
3. Any smart contract associated with an address that can be spent on the username will appear in the asset list, which provides more information on the smart contract’s token limit, transaction hash, and token standards.
4. Click the “Connect to Web3” button to connect to the wallet.
5. After confirming the connection, select the contract to be revoked.
How to revoke token approval and license for smart contracts on Ethereum
Here are the steps you usually take when revoking a smart contract on the Ethereum mainnet:
Step 1: Undo the access tool
Users can use a variety of third-party revocation tools to track and revoke smart contracts connected to their addresses.Connect to any of the following websites to start the process:
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approved.zone: Ethereum
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Revoke: Multiple networks
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EverRise: Multiple networks
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Ethallowance: Ethereum
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Unrekt: Multiple networks
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Beefy.finance: BNB Smart Chain
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Etherscan: Ethereum
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Cointool: Multiple networks
Step 2: Connect the wallet
Once connected to the website, search and click the “Connect Wallet” button.When connecting websites to your wallet, make sure they are on the same network, as the undo access tool can only work in one chain.
For example, if you connect to the Ethereum mainnet, you cannot revoke the Polygon smart contract because only Ethereum smart contracts are supported and displayed.
Step 3: Choose a smart contract
The Smart Contract Tool will display all compatible smart contracts, showing their access rights and spending restrictions.Users should choose those contracts they want to revoke.If you are not sure, select All and grant new permissions the next time you launch each DApp.
Step 4: Revoke access
Click the “Revoke” button to pay the transaction fee and wait for a minute or two to complete the transaction.Log out and log back into the website to confirm that the revocation of the transaction was successful (smart contracts should not appear in the list).
Will revoking token access also terminate the DeFi policy?
No.Users will retain their positions in decentralized finance (DeFi) strategies such as pooling, staking, and lending, so that they can continue to receive rewards.However, it can have a significant impact on them, depending on the situation and the structure of the strategy.
In the DeFi ecosystem, users usually grant smart contracts access to their tokens to enable various functions such as transactions, lending, or staking.If a user revokes this access, the smart contract will no longer be able to move or manage the user’s tokens on their behalf.
This operation may undermine the ongoing strategy that relies on the ability to interact with the token.However, the underlying DeFi policy is not terminated, but is paused or inactive until access is granted again or the policy is adjusted.
Is disconnecting the wallet from the project the same as canceling the fund use permission?
No, they are not the same thing.Disconnecting the wallet from the project will only cancel permissions to allow other users to view their token balances, public addresses, and past activities, and will stop starting transactions.But please note that this will not prevent the transaction from being executed.
On the other hand, revoking permissions to use funds means revoking permissions to access and move wallet content on DApps.
