Mojo-V: Secret Computation for RISC-V

Mojo-V (pronounced “mojo-five”) is a new RISC-V extension that introduces privacy-oriented programming capabilities for RISC-V. Mojo-V implements secret computation, enabling secure, efficient, and data-oblivious execution without reliance on fragile software and programmer trust. By sequestering sensitive data in dedicated secret registers and encrypting memory under a third-party key, Mojo-V prevents disclosures and enforces computation that is both blind (no direct disclosures) and silent (no side channel leakage). The design integrates seamlessly into the existing RISC-V ISA with only a mode bit and four new instructions, enforced entirely at decode. Early results show near-native execution speeds while offering over 5-7 orders of magnitude performance improvement compared to fully homomorphic encryption (FHE), with a clear roadmap for integration into CPUs, GPUs, and specialized accelerators.

To learn more...

• Here is an intro video describing Mojo-V: https://www.youtube.com/watch?v=HUT46TcNyyM
• Slides that give an overview of the Mojo-V project: https://drive.google.com/file/d/1VVzZqYHvQgnKMgXZjg7I_cX2GzF7awSN

The current Mojo-V ISA Extension Specification (release 0.92):

• [In PDF format.] (https://drive.google.com/file/d/1pargKATFoQdy94i6bI3P_9mfNA_GsYSw)

To contact the developers of Mojo-V:

• Email: [email protected]

🧩 Mojo-V Reference Platform — Release 0.92

🚧 Project Status

The Mojo-V reference platform release 0.92 implements secret integer and floating-point computation using a fixed symmetric key cipher. Mojo-V supports three encryption modes: fast, strong, and proof-carrying. As of this release, 64-bit secret computation is fully secretized and this early reference platform can be used for software development and red-teaming. Additional capabilities will be rolled out in future releases, including PKI support, LLVM compiler support, 32-bit RISC-V support, VIP-Bench benchmarks support, etc.

Specification Version: 0.92 (November 2025)
Contact: [email protected]

Current components

1. Mojo-V ISA Spec v0.92
   • released in doc/
2. Spike (Instruction Set Simulator) Implementation
   • Mojo-V integrated into riscv-isa-sim, nearly feature-complete
   • Missing only: Public-Key Infrastructure (PKI) support (currently uses fixed keys with a Simon-128 cipher)
   • To run Spike with Mojo-V extensions enabled, add the --isa=rv64gc_zicond_zkmojov_zicntr flag when running spike
3. Mojo-V Bringup-Bench Benchmarks
   • Hand-coded examples (e.g., bubble-sort) showing Mojo-V working secret computation
   • Full battery of security tests for RV64GC+Mojo-V

Note, the remainder of the Bringup-bench benchmarks have NOT been ported to Mojo-V, as yet.

⚙️ Building and Running the Mojo-V Reference Platform

A. Install a RISC-V LLVM Compiler

You’ll need an LLVM-based RISC-V cross-compiler capable of producing RV64GC binaries.

Here is a good place to start: https://clang.llvm.org/get_started.html

B. Clone the Mojo-V Repository

git clone https://github.com/toddmaustin/mojo-v.git
cd mojo-v

C. Build the RISC-V Spike simulator with Mojo-V Support

sudo apt-get install device-tree-compiler libboost-regex-dev libboost-system-dev
cd riscv-isa-sim
mkdir build
cd build
../configure --prefix=$RISCV
make

D. Build and Run Mojo-V Bringup-Bench Benchmark Tests

1. Build the Spike device driver

   cd bringup-bench/target
   make

2. Configure your compiler

   Edit ../Makefile and set TARGET_CC for the mojov target to the location of your LVM Clang-based RISC-V compiler.

3. Build and test

   cd ..                # go to the top-level bringup-bench directory
   make mojov-tests     # run all Mojo-V tests

   As an alternative, you can run an individual benchmark by going into its directory and running the following command.

   cd ../mojov-test
   make TARGET=mojov clean build test

🧪 Mojo-V Bringup-Bench Benchmarks Overview

Program	Description
mojov-test	Intro example from slides
mojov-test1	Secret-register and encrypted-memory semantics tests
mojov-test2	Hand-coded data-oblivious integer bubble-sort benchmark with Mojo-V fast encryption (int,fast)
mojov-test3	Hand-coded data-oblivious floating-point bubble-sort benchmark with Mojo-V fast encryption (fp,fast)
mojov-test4	Hand-coded data-oblivious integer bubble-sort benchmark with Mojo-V strong encryption (int,strong)
mojov-test5	Hand-coded data-oblivious floating-point bubble-sort benchmark with Mojo-V strong encryption (fp,strong)
mojov-pctests	Hand-coded integrity checking test suite for RV64GC+Mojo-V that includes positive and negative tests for Mojo-V's proof-carrying encryption format (proofcarrying)
mojov-sectests	Hand-coded security test suite for RV64GC+Mojo-V that includes 130 pos + 245 neg tests == 375 total (int,fp,fast,strong)

All test benchmarks are hand-coded assembly programs demonstrating Mojo-V ISA rules and security semantics. The other Bringup-Bench benchmarks have not yet been ported to Mojo-V.

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Code Licensing

All of the Mojo-V related code in this repo is released under the license of the tool it modified (e.g., Spike, LLVM, Bringup-Bench). Please see the tools' respective directories for licensing details.

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💬 Questions & Feedback

We welcome contributions, bug reports, and suggestions!

📧 Email: [email protected]
🌐 Project Home: https://github.com/toddmaustin/mojo-v