zkDaily - 2026-08-21

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ZKP Frontier Tracker 🎯

Fri

08.21

2026

Verifiable Compression of Images

Paper

https://eprint.iacr.org/2026/1717

JPEGC2PAKZHPoseidon

Zhang et al. proposed SPEG, the first practical proof system supporting the full image transmission pipeline on personal devices. It supports JPEG compression while preserving C2PA signatures, with optimizations for non-algebraic encoding and floating-point arithmetic. Proving FHD images takes 47s (Poseidon) or 2s (fast mode). Also fixes a security gap in VIMz.

NotesNotes要点

SPEG is the first practical proof system supporting the full image transmission pipeline.
It supports JPEG compression while verifying C2PA signatures.
Offers a Poseidon-compatible mode and a fast KZH-based mode.
Key optimizations: moving non-algebraic JPEG encoding out of the circuit and avoiding range checks in floating-point arithmetic.
FHD proving takes 47s (Poseidon) and 2s (fast mode).
Identifies and fixes a VIMz security gap that allows forging proofs for unauthorized images.

Collected by @icerdesign

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Q&A Deep Dive 💬

Fri

08.21

2026

Why is JPEG compression hard to prove in ZK?

JPEG involves non-algebraic operations and floating-point arithmetic, which are inefficient to express in circuits.

How does SPEG avoid handling JPEG encoding in-circuit?

It moves non-algebraic JPEG encoding outside the proving circuit and verifies only the necessary properties.

How does the paper handle secure floating-point arithmetic?

It avoids range checks in floating-point arithmetic, moving non-algebraic parts outside the circuit.

Prompted by @icerdesign