Phantom is a prototype fully encrypted RISC-V virtual machine that executes encrypted RISC-V binaries on encrypted inputs.

It enables black-box execution of any RISC-V program, allowing developers to write code with hidden instructions, constants, and states. This opens the door to new types of applications.

Developers write their programs in Rust, which are then compiled into RISC-V binaries. These binaries are transformed into a polynomial representation, optimized for execution within the plaintext space of RLWE-base FHE. These polynomials are then encrypted, producing the encrypted program, which can then be executed by the Phantom executor on arbitrary encrypted and/or plaintext inputs.

To use, we recommend to look at full end to end examples in compiler-tests directory. In particular, the sybil-resistant-id example.

The Phantom executor is a collection of FHE circuits that, collectively, simulate a RISC-V virtual machine. It is implemented in the ./fhevm directory, with specifications detailed in ./fhevm/doc. A poster also provides a high-level overview of the end-to-end execution flow.

Both the implementation and specifications are actively evolving and subject to change. We encourage feedback and questions — feel free to open an issue.

Phantom is still in active development and currently implements only a prototype of the polynomial executor. All circuits are built using plaintext polynomials, allowing for accurate runtime estimations of a single cycle. In the coming months, these plaintext circuits will be replaced with versions that operate on encrypted polynomials.

Phantom may resemble program obfuscation, but it is not. However, it could potentially be used for practical program obfuscation in the future, by offloading the main computation to an FHE-scheme and limiting the obfuscation to a conditional decryptor).

After cloning the repository, run the following script at the root

./setup.sh

The script clones pouply, our FHE backend library, and initializes the submodules. poulpy is cloned at .., that is parent directory of phantom.

After this you're ready to run examples under compiler-tests.

• We thank authors of nexus-zkvm for their runtime, sdk crate using which, as a reference, we've implemented our runtime, compiler crates.
• We thank authors of risc0 and nexus-zkvm from which we've taken alloc.rs implementation.