Apple enhances iMessage security, making it resistant to quantum computer attacks

Apple is future-proofing its texting platform iMessage, protecting it against sophisticated quantum computing attacks. Towards this end, Apple has introduced PQ3, a post-quantum cryptographic protocol that advances the state of the art of end-to-end secure messaging. As PQ3 features compromise-resilient encryption and extensive defences against even highly sophisticated quantum attacks, it is the first messaging protocol to reach what we call Level 3 security.

Apple in a blog post explains that historically, messaging platforms have used classical public key cryptography, such as RSA, Elliptic Curve signatures, and Diffie-Hellman key exchange, to establish secure end-to-end encrypted connections between devices. All these algorithms are based on difficult mathematical problems that have long been considered too computationally intensive for computers to solve. However, the rise of quantum computing threatens to change the equation as a sufficiently powerful quantum computer could solve these classical mathematical problems in fundamentally different ways, and therefore — in theory — do so fast enough to threaten the security of end-to-end encrypted communications.

Even though such quantum computers don’t yet exist, Apple understands that extremely well-resourced attackers can already prepare for their possible arrival by taking advantage of the steep decrease in modern data storage costs.  With the new update, Apple is aiming to mitigate the risk of attack scenario - Harvest Now, Decrypt Later, where attackers can collect large amounts of today’s encrypted data and file it all away for future reference, and decrypt when they acquire a quantum computer in the future.

For this, instead of simply replacing an existing algorithm with a new one, Apple has rebuilt the iMessage cryptographic protocol from the ground up to advance the state of the art in end-to-end encryption. This will introduce post-quantum cryptography from the start of a conversation, so that all communication is protected from current and future adversaries. It will also mitigate the impact of key compromises by limiting how many past and future messages can be decrypted with a single compromised key, and use a hybrid design to combine new post-quantum algorithms with current Elliptic Curve algorithms, ensuring that PQ3 can never be less safe than the existing classical protocol. It will also include amortizing message size to avoid excessive additional overhead from the added security. Lastly, use formal verification methods to provide strong security assurances for the new protocol.

Apple has always been focused on consumer privacy and even when the iMessage was launched in 2011, it was the first widely available messaging app to provide end-to-end encryption by default. Over the years, Apple has significantly upgraded its cryptography  with the most recent being strengthening the iMessage cryptographic protocol in 2019 by switching from RSA to Elliptic Curve cryptography (ECC), and by protecting encryption keys on device with the Secure Enclave, making them significantly harder to extract from a device even for the most sophisticated adversaries.