To secure data integrity when using a Trusted Execution Environment (TEE) with a smart contract, follow these steps:

Pre-Validate Data: Always verify the data before it enters the TEE. Use cryptographic methods like digital signatures or hashes to ensure the data is authentic and hasn’t been tampered with. This check is crucial to prevent compromised data from reaching the TEE.

Use Secure Communication: Protect the data while it's being transmitted to the TEE. Use encryption protocols like TLS to secure the data in transit. This prevents anyone from intercepting or altering the data during transmission.

Leverage TEE Features: Many TEEs support integrity checks like remote attestation. Use this feature to confirm that the TEE is secure and hasn’t been altered. This ensures that the data will be processed in a trusted environment.

Enable Logging: Set up detailed logging to track every interaction with the TEE. This allows you to monitor and audit data entering and exiting the TEE. Logs can help you detect issues and verify that data hasn’t been tampered with during processing.

By using pre-validation, secure communication, TEE-specific features, and logging, you can effectively ensure data integrity when working with TEEs and smart contracts.