Best Practices

This guide outlines key best practices for developing with CoFHE, based on recommendations from our development team.

Security Considerations

Always consider information leakage: Before decrypting data, evaluate what information you're exposing, how your code branches based on decrypted values, and what an observer might learn.
Minimize decryption operations: Only decrypt when absolutely necessary and after all sensitive computations are complete.
Always Update Permissions: Remember to call FHE.allowThis() after modifying any encrypted value that needs to be accessed later:
```
counter = FHE.add(counter, FHE.asEuint32(1));
FHE.allowThis(counter);  // Required!
```

Remember there is no secure code branching with FHE: Decrypting to make branching decisions is generally a bad practice.
Use constant-time algorithms: Design your code to follow the same execution path regardless of encrypted values.
Prefer FHE.select over conditional logic: Use built-in selection operations rather than decrypting for if/else decisions. Since conditional branching doesn't work with encrypted values, use FHE.select() instead:
```
// Instead of: if (condition) { result = a; } else { result = b; }
result = FHE.select(condition, a, b);
```
Read more about conditions here.

Minimize FHE operations: Each operation adds computational overhead.
Use the minimum bit-width necessary: Choose the smallest integer type that can safely represent your data (e.g., euint32 instead of euint64 when possible).

Reuse Encrypted Constants - gas saver: Encrypt constant values once and reuse them to save gas:

// Good practice
euint32 ONE = FHE.asEuint32(1);
FHE.allowThis(ONE);

// Later in the code
counter = FHE.add(counter, ONE);

Implement loading indicators in your UI: Due to CoFHE's asynchronous nature, operations may take time to complete.
Use progress indicators: Show spinners, progress bars, or status messages to inform users when operations are in progress.
Consider state management: Design your application to handle pending states gracefully.