Post-Quantum Cryptography

In the last episode of PING for 2024, APNIC’s Chief Scientist Geoff Huston discusses the shift from existing public-private key cryptography using the RSA and ECC algorithms to the world of ‘Post Quantum Cryptography. These new algorithms are designed to withstand potential attacks from large-scale quantum computers and are capable of implementing Shor’s algorithm, a theoretical approach for using quantum computing to break the cryptographic keys of RSA and ECC. Standards agencies like NIST are pushing to develop algorithms that are both efficient on modern hardware and resistant to the potential threats posed by Shor’s Algorithm in future quantum computers. This urgency stems from the need to ensure ‘perfect forward secrecy’ for sensitive data — meaning that information encrypted today remains secure and undecipherable even decades into the future. To date, maintaining security has been achieved by increasing the recommended key length as computing power improved under Moore’s Law, with faster processors and greater parallelism. However, quantum computing operates differently and will be capable of breaking the encryption of current public-private key methods, regardless of the key length. Public-private keys are not used to encrypt entire messages or datasets. Instead, they encrypt a temporary ‘ephemeral’ key, which is then used by a symmetric algorithm to secure the data. Symmetric key algorithms (where the same key is used for encryption and decryption) are not vulnerable to Shor’s Algorithm. However, if the symmetric key is exchanged using RSA or ECC — common in protocols like TLS and QUIC when parties lack a pre-established way to share keys — quantum computing could render the protection ineffective. A quantum computer could intercept and decrypt the symmetric key, compromising the entire communication. Geoff raises concerns that while post-quantum cryptography is essential for managing risks in many online activities — especially for protecting highly sensitive or secret data—it might be misapplied to DNSSEC. In DNSSEC, public-private keys are not used to protect secrets but to ensure the accuracy of DNS data in real-time. If there’s no need to worry about someone decoding these keys 20 years from now, why invest significant effort in adapting DNSSEC for a post-quantum world? Instead, he questions whether simply using longer RSA or ECC keys and rotating key pairs more frequently might be a more practical approach. PING will return in early 2025 This is the last episode of PING for 2024, we hope you’ve enjoyed listening. The first episode of our new series is expected in late January 2025. In the meantime, catch up on all past episodes.