Apple Computer has implemented Post Quantum Cryptography (PQC) support within the iMessage app of its next operating system updates iOS 17.4, iPadOS 17.4, macOS 14.4, and watchOS 10.4 scheduled to be released in early March. Apple calls this feature PQ3 and it has several interesting features. In this implementation they are taking a conservative approach by implementing a hybrid cryptography protocol that includes both their current elliptic curve algorithms along with the ML-KEM (Kyber) being standardized by NIST. This will ensure that even if an issue were to be found in the future in ML-KEM, the encryption would still be at least as secure as the previous versions of iMessage that use elliptic curve encryption alone.
Many implementations will use a PQC algorithm for the initial key establishment and then use a symmetric encryption algorithm like AES to encrypt the message. However, Apple’s PQ3 will use PQC to secure both the initial key establishment and the ongoing message exchange. Their protocol also implements a periodic rekeying mechanism to ensure that if a previous key were to be compromised, future messages can still be protected. Apple indicates that with these features they are implementing what is called Level 3 securing and indicate their belief that this PQ3 implementation implements the strongest security properties of any at-scale messaging protocol in the world.
Apple has posted a detailed blog that describes the implementation of this new quantum safe security protocol in iMessage and it can be viewed here.
February 23, 2024