Quantum Use Case #68: Quantum-safe identity and certificates

Short answer: This use case involves migrating digital identity systems, such as Verifiable Credentials and HTTPS certificates, to post-quantum cryptographic algorithms to prevent forgery and impersonation by future quantum computers. It is a realistic and active area of standardization, with major technology providers and standards bodies already addressing the performance and security implications of larger quantum-resistant signatures.

The Threat to Current Identity Systems

Current digital identity infrastructure relies heavily on cryptographic algorithms that are vulnerable to quantum attacks. Specifically, Verifiable Credentials (VCs) depend on digital signatures to guarantee the integrity and authenticity of their data. Algorithms commonly used for these signatures, including RSA, EdDSA, and ECDSA, can be efficiently broken by a sufficiently powerful quantum computer. If such a machine were available, malicious actors could forge VCs and impersonate their holders or issuers. This vulnerability extends beyond simple credentials to the broader digital universe, where conventional encryption methods like RSA and Elliptic Curve Cryptography (ECC) safeguard most digital communications.

The risk is not limited to future scenarios where quantum computers are fully operational. Researchers and industry observers note that "Harvest Now, Decrypt Later" style attacks already target long-life data and long-life devices. In this model, an adversary captures encrypted data today and stores it until a quantum computer is powerful enough to decrypt it. Because identity documents and certificates often have long lifespans, they are particularly susceptible to this threat. Consequently, many experts argue that the post-quantum era has effectively already begun, necessitating proactive migration to quantum-safe techniques before commercially viable quantum computers arrive.

Challenges in Certificate Transparency

A specific challenge arises in the context of HTTPS and Certificate Transparency (CT). Quantum-resistant cryptography typically introduces larger signature sizes compared to classical methods. This increased size creates performance and bandwidth challenges for TLS connections that rely on CT. To address these issues, the Internet Engineering Task Force (IETF) recently created a working group known as PKI, Logs, And Tree Signatures (PLANTS). This group aims to mitigate the efficiency problems caused by the increased size of quantum-resistant cryptography in TLS connections.

Major technology providers are actively participating in this standardization effort. For instance, Google has announced a new program in Chrome to make HTTPS certificates secure against quantum computers. This initiative is part of a broader call to action to secure quantum computing and address the challenges introduced by quantum-resistant cryptography. The goal is to ensure the scalability and efficiency of the ecosystem while transitioning to quantum-safe protocols. These efforts are currently at the research and standardization stage, focusing on how to implement these larger signatures without degrading the performance of the web.

Implications for Verifiable Credentials

In the domain of Verifiable Credentials, the adoption of post-quantum cryptographic techniques is viewed as essential to protect against the threat of quantum attacks. VCs are foundational to securing digital communication and data, and their reliance on digital signatures makes them a primary target for migration. The documentation from IOTA, a developer-focused platform, highlights that current algorithms are vulnerable and that adopting post-quantum techniques is necessary to maintain the authenticity of credentials.

The transition involves replacing classical signature schemes with quantum-resistant alternatives. However, this is not merely a drop-in replacement. The larger output sizes of post-quantum signatures can impact storage and transmission efficiency. Therefore, the development of quantum-safe identity systems requires careful consideration of both security and performance. Researchers have proposed various approaches to handle these larger signatures, but widespread operational adoption is still pending. The focus remains on ensuring that the integrity and authenticity of digital identities are preserved against future quantum capabilities.

Current Status and Research Stage

It is important to clarify that while the threat is real and the standardization process is underway, most implementations of quantum-safe identity and certificates are at the research or early standardization stage. Major announcements, such as those from Google regarding Chrome, represent steps toward securing the ecosystem and addressing performance challenges, rather than a declaration that all web traffic is already protected by quantum-safe certificates. Similarly, discussions about "Q-Day" and the arrival of commercially viable quantum computers are framed as future events that will necessitate the completion of these migrations.

The current landscape involves parallel efforts to standardize post-quantum algorithms and to integrate them into existing protocols like TLS and PKI. The PLANTS working group exemplifies this standardization activity. Until these standards are finalized and widely deployed, the ecosystem remains in a transitional phase. Users and developers should be aware that while the tools are being developed, the full protection against quantum attacks for identity and certificates is not yet universally operational. The emphasis is on preparing the infrastructure to withstand the eventual arrival of quantum computing capabilities.

FAQ

Are current digital signatures vulnerable to quantum computers?

Yes. Algorithms such as RSA, EdDSA, and ECDSA, which are currently used for digital signatures in Verifiable Credentials and other identity systems, are vulnerable to quantum attacks. A sufficiently powerful quantum computer could efficiently break these signatures, allowing malicious actors to forge credentials and impersonate holders or issuers.

What is the "Harvest Now, Decrypt Later" attack?

This is a style of attack that targets long-life data and long-life devices. An adversary captures encrypted data today and stores it, waiting for a quantum computer to become powerful enough to decrypt it. Because identity documents and certificates often have long lifespans, they are particularly at risk from this type of delayed decryption attack.

How does the IETF address the size of quantum-resistant signatures?

The IETF has created a working group called PKI, Logs, And Tree Signatures (PLANTS). This group aims to address the performance and bandwidth challenges introduced by the increased size of quantum-resistant cryptography in TLS connections that require Certificate Transparency. The goal is to ensure scalability and efficiency while adopting quantum-safe protocols.

Is quantum-safe HTTPS already fully deployed?

No. While major providers like Google have announced programs to make HTTPS certificates secure against quantum computers and have shared calls to action, these efforts are part of an ongoing standardization and research process. The ecosystem is not yet fully migrated, and the focus remains on addressing the performance and bandwidth challenges of larger signatures before widespread operational adoption.

Why are Verifiable Credentials a priority for post-quantum migration?

Verifiable Credentials rely on digital signatures to ensure the integrity and authenticity of their data. Since current signature algorithms are vulnerable to quantum attacks, adopting post-quantum cryptographic techniques is essential to prevent forgery and impersonation. Protecting these credentials is considered foundational to securing digital communication and data in the post-quantum era.