Paper 2026/618 Original: eprint.iacr.org/2026/618 ↗

QCAP: A Quantum Canary Address Generation Protocol

Abstract

The advent of quantum computing poses a fundamental threat to classical cryptographic assumptions. While algorithms such as RSA and Elliptic-Curve Cryptography are secure against classical adversaries, they would be efficiently broken by a sufficiently powerful quantum adversary. Yet, despite rapid industrial and academic progress, the timeline for achieving a Cryptographically Relevant Quantum Computer (CRQC) remains uncertain and opaque. In this work, we propose a mechanism to monitor quantum capabilities through economic incentives. We introduce QCAP, a trustless distributed protocol for deploying a quantum canary address alert. QCAP enables the creation of publicly auditable cryptographic challenges whose solutions would reveal the existence of quantum computers capable of breaking the Elliptic Curve Discrete Logarithm problem. The protocol is decentralized, secure, efficient, and verifiable, featuring adjustable difficulty and native Bitcoin compatibility. A proof-of-concept implementation demonstrates the feasibility of QCAP as a Bitcoin-based early-warning system for the emergence of quantum computational power.