> For the complete documentation index, see [llms.txt](https://docs.zama.org/tfhe-rs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zama.org/tfhe-rs/fhe-computation/tooling/debug.md).

# Debugging

This document explains a feature to facilitate debugging.

Starting from **TFHE-rs 0.5**, [trivial ciphertexts](/tfhe-rs/fhe-computation/advanced-features/trivial-ciphertext.md) introduce a new feature to facilitate debugging. This feature supports a debugger, print statements, and faster execution, significantly reducing waiting time and enhancing the development pace of FHE applications.

{% hint style="warning" %}
Trivial ciphertexts are not secure. An application released/deployed in production must never receive trivial ciphertext from a client.
{% endhint %}

To use this feature, simply call your circuits/functions with trivially encrypted values that are created using `encrypt_trivial`(instead of real encryptions that are created using `encrypt`):

```rust
use tfhe::prelude::*;
use tfhe::{set_server_key, generate_keys, ConfigBuilder, FheUint128};


fn mul_all(a: &FheUint128, b: &FheUint128, c: &FheUint128) -> FheUint128 {
    // Use the debug format ('{:?}'), if you don't want to unwrap()
    // and panic if the value is not a trivial.
    println!(
        "a: {:?}, b: {:?}, c: {:?}", 
        a.try_decrypt_trivial::<u128>(),
        b.try_decrypt_trivial::<u128>(),
        c.try_decrypt_trivial::<u128>(),
    );
    let tmp = a * b;
    
    println!("a * b = {:?}", tmp.try_decrypt_trivial::<u128>());

    tmp * c
}


fn main() {
    let (cks, sks) = generate_keys(ConfigBuilder::default().build());
    
    set_server_key(sks);
    
    let a = FheUint128::encrypt_trivial(1234u128);
    let b = FheUint128::encrypt_trivial(4567u128);
    let c = FheUint128::encrypt_trivial(89101112u128);
    
    // since all inputs are trivially encrypted, this is going to be
    // much faster
    let result = mul_all(&a, &b, &c);
}
```

This example is going to print:

```console
a: Ok(1234), b: Ok(4567), c: Ok(89101112)
a * b = Ok(5635678)
```

If any input to `mul_all` is not a trivial ciphertext, the computations will be done 100% in FHE, and the program will output:

```console
a: Err(NotTrivialCiphertextError), b: Err(NotTrivialCiphertextError), c: Err(NotTrivialCiphertextError)
a * b = Err(NotTrivialCiphertextError)
```

Using trivial encryptions as input, the example runs in **980 ms** on a standard 12-core laptop, compared to **7.5 seconds** on a 128-core machine using real encryptions.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.zama.org/tfhe-rs/fhe-computation/tooling/debug.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.