TokenScript
TokenScript is a JavaScript / XML framework for blockchain token which creates a user-interface layer between a blockchain, APIs and user devices.
TokenScript allows token issuers and other trusted authorities to enrich a given token with a wide set of information, rules and functionalities. With TokenScript wallets and webservices can easily, securely and privately implement a token with all its functions, both onchain and offchain, without the need to understand the underlying smart contract.
You can learn more about TokenScript framework using the documentation here.
Security
One of the main advantages of TokenScript is the use of XML digital signatures to ensure the TokenScript is valid for the contracts that it interacts with. DApp are traditionally centralised services, that are hosted by a single entity. In contrast, due to the use of digital signatures, TokenScript applications can be distributed and hosted anywhere without impacting user security.
To summarise, TokenScript has the following security principals:
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Containment - TokenScripts are executed in a sandboxed iFrame or webview. This prevents potentially malicious scripts from accessing user-agents such as a wallet or DApp. The only way a TokenScript can interact with the user-agent is through a defined API provided by the TokenScript Engine & Card SDK.
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Verification - For a TokenScript to have a valid signature, it must be signed by the owner or deployer of the Token contract it is used with, or another trusted key provided by the user-agent. TokenScripts can only interact freely with contract that it is signed for. If it tries to interact with another contract (i.e. an approval for wETH) the TokenScript engine will display a warning to the user before sending the TX.
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Whitelisting - Sometimes it is desirable for the user-agent to have more control over what TokenScripts can be loaded. In this case a whitelist can be specified ensuring only reviewed TokenScripts can be loaded into the user-agent. Alternatively a warning can be shown to the user, letting them decide if they want to run an unreviewed TokenScript.