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Jolt

4 parts September 2024 – May 2026 38 min in total Giorgio Dell'Immagine · Suneal Gong · Imam Al-Fath · Minsun Kim
  1. Part 1

    A challenge on the Jolt zkVM

    Last weekend, we had a blast crafting challenges for a CTF event at the MOCA Italian hacker camp. One cryptography challenge, "2+2=5," involved the Jolt zkVM and a RISC-V program. In this post, we share the ins and outs of the challenge, the clever use of a modified Jolt library, and how we managed to prove an invalid execution without triggering verification alarms. Get ready to dive into the world of Jolt and pick up some nifty insights on exploiting cryptographic systems like a true hacker.

    Giorgio Dell'Immagine September 24, 2024 10 min Read →
  2. Part 2

    Improving the Security of the Jolt zkVM

    We recently explored a16z’s Jolt zkVM to bolster its security, discovering significant bugs in the process. Our findings revealed vulnerabilities that could allow malicious provers to forge proofs, highlighting the crucial role of manual reviews in catching these issues. Jolt, with its unique approach using the Lasso lookup technique, aims to improve prover efficiency and system scalability. With these bugs now fixed, this work underscores the importance of thorough audits in ensuring the reliability of advanced zkVM technology. Stay tuned as we continue to delve into zkVM security insights.

    Suneal Gong, Imam Al-Fath November 19, 2024 6 min Read →
  3. Part 3

    A Technical Dive into Jolt: The RISC-V zkVM

    In our latest post, we take you inside the workings of Jolt, a zero-knowledge virtual machine for the RISC-V architecture. This post breaks down the three main components that prove execution correctness: instruction lookup, offline memory checking, and the Rank-1 Constraint System (R1CS). By exploring these elements, you'll get a grasp on how Jolt ensures VM execution is accurate and reliable, using innovative methods like Lasso lookup arguments and the Spartan protocol. Join us as we unravel this cutting-edge zkVM, which not only promises simplicity but also the potential for exciting advancements.

    Imam Al-Fath December 09, 2024 17 min Read →
  4. Part 4

    Breaking Jolt’s Verifier with an Unbound Uni-Skip Claim

    We found a critical soundness bug in Jolt’s transparent verifier that allowed a forged proof for an invalid execution to verify. The issue was fixed quickly after disclosure, and the full PoC and write-up are available in the linked repository.

    Minsun Kim May 09, 2026 5 min Read →
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