Private Proof Delegation

# Update PPD project plan Original project plan: https://hackmd.io/qdYZCxweQmix8ezdh7l-Aw?view ## Changed milestone As we’ve deepened our understanding of the field, we are refining the second milestone to focus on a specific FHE-based private proof delegation protocol and define concrete deliverables around it. Additionally, we are adjusting the project timeline due to an unexpected reduction in team size. ### Milestone : Implementation and Benchmarking of FHE-SNARK #### Milestone Description The third milestone (June–August 2025) focuses on implementing and analyzing core components of the FHE-SNARK protocol described in [ePrint 2025/302](https://eprint.iacr.org/2025/302). Our primary goal is to uncover and characterize the practical costs and trade-offs inherent in this protocol — especially those that are not precisely captured in the original theoretical analysis. This includes: * Implementation of the polynomial commitment scheme over hybrid values, where the committed witness may contain both plaintext and FHE-encrypted elements. * Construction of the associated polynomial interactive oracle proof (PIOP) protocol adapted to the FHE setting. * Composition of these components into an initial end-to-end FHE-SNARK proving pipeline. * Identification and evaluation of real-world bottlenecks and trade-offs — for example, between computation time and network bandwidth. A particular focus will be placed on quantifying the hidden costs of protocol choices. For instance, reducing computation load on the FHE server may require performing witness extension on the client side, followed by encryption and transmission of the full extended witness. This leads to a massive increase in ciphertext size, placing high demands on bandwidth and memory. Such trade-offs are not fully quantified in the paper and need to be carefully assessed in practical deployments. Once a working pipeline is in place, we will apply basic optimizations such as SIMD operations, ciphertext packing, and batching strategies to evaluate their impact on overall performance. Lower-priority tasks (to be pursued only if time permits) include: * Witness extension procedures over encrypted values, possibly requiring an FHE scheme beyond BFV. * Proof of decryption mechanisms, which are essential for supporting publicly verifiable proofs. #### Deliverables * Working implementation of the polynomial commitment and PIOP components over hybrid values, composed into a functional FHE-SNARK proving pipeline. * Benchmark report evaluating: * End-to-end proving time * Bandwidth consumption * Hardware requirements * Analytical report detailing hidden costs and trade-offs observed during implementation: * E.g., computation–bandwidth trade-offs introduced by witness extension * Overhead of ciphertext handling under realistic network conditions * Optional: Partial support for witness extension and proof of decryption, if achievable within the milestone timeframe.