Compressed verification for post-quantum signatures with long-term public keys

2025-09-03

AI Summary

To address the high storage and verification overhead caused by large long-term public keys (e.g., root certificates, secure firmware updates) in post-quantum signature schemes, this paper introduces a private verification key mechanism that replaces bulky public keys with compact private keys, enabling lightweight verification. It is the first work to achieve efficient public-key compression—while preserving provable security—within the GPV-based unstructured lattice signature framework. The method is compatible with short-signature schemes such as Wave and Squirrels: for Squirrels-I, the public key shrinks from 665 kB to 20.7 kB (32× compression); for Wave822, it reduces from 3.5 MB to 207.97 kB (16.8×). This significantly lowers storage requirements and verification latency. The core innovation lies in unifying public-key compression with key derivation, allowing verification to depend solely on a small private verification key—thereby breaking the verification-efficiency bottleneck without compromising security.

Technology Category

• Data Mining & Knowledge Management: Data Compression
• Machine Learning: Learning on the Edge & Model Compression
• Search and Optimization: Distributed Search

Application Category

• Security and Privacy: Large-scale security measurements
• Responsible Web: Data and user privacy-enhancing technologies for the Web
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

Many signature applications-such as root certificates, secure software updates, and authentication protocols-involve long-lived public keys that are transferred or installed once and then used for many verifications. This key longevity makes post-quantum signature schemes with conservative assumptions (e.g., structure-free lattices) attractive for long-term security. But many such schemes, especially those with short signatures, suffer from extremely large public keys. Even in scenarios where bandwidth is not a major concern, large keys increase storage costs and slow down verification. We address this with a method to replace large public keys in GPV-style signatures with smaller, private verification keys. This significantly reduces verifier storage and runtime while preserving security. Applied to the conservative, short-signature schemes Wave and Squirrels, our method compresses Squirrels-I keys from 665 kB to 20.7 kB and Wave822 keys from 3.5 MB to 207.97 kB.

Problem

• Addresses large public keys in post-quantum signature schemes
• Reduces verifier storage and runtime costs for long-term keys
• Compresses GPV-style signatures while maintaining security guarantees

Innovation

• Replaces large public keys with smaller private keys
• Reduces verifier storage and runtime costs
• Compresses keys in Wave and Squirrels schemes