The impact of quantum computing on existing asymmetric cryptography, such as the widely used RSA and ECC algorithms, is a significant concern. Quantum computers have the potential to break these cryptographic algorithms by efficiently factoring large numbers or solving the elliptic curve discrete logarithm problem.
If we transition to post-quantum cryptography (PQC) algorithms before large-scale, fault-tolerant quantum computers become a reality, future SSL/TLS communications can be protected against quantum attacks. PQC algorithms are designed to resist attacks from both classical and quantum computers. The ongoing research and standardization efforts aim to identify and develop PQC algorithms that are secure against quantum attacks.
However, transitioning to PQC algorithms does not directly address the security of previously recorded SSL communication. The encryption used in past SSL sessions, which employed classical cryptographic algorithms, would remain vulnerable to attacks by future quantum computers. This implies that an attacker with a large-scale quantum computer could potentially decrypt and access the content of past SSL communications that were recorded and stored.
The potential consequences of such a scenario depend on several factors:
Data Retention: The extent to which past SSL communications are recorded and retained by organizations or entities would determine the scale of the impact. If communications are stored for long periods, a larger volume of data could be at risk.
Sensitivity of the Data: The nature of the information contained in the past SSL communications would determine the potential risks associated with its decryption. Highly sensitive or confidential data, such as financial information or personal data, would pose more significant concerns if exposed.
Mitigation Measures: Organizations may employ additional security measures to protect sensitive data, such as forward secrecy (where session keys are ephemeral) or secure key management practices. These measures could reduce the impact of future decryption attempts, as older session keys may become obsolete and less relevant.
While the potential decryption of past SSL communication by future quantum computers poses a theoretical risk, it's important to note that the timeline for the development of large-scale, fault-tolerant quantum computers and their practical application is still uncertain. Furthermore, organizations can proactively adopt best practices, implement mitigation strategies, and consider the security implications of long-term data storage to minimize potential risks associated with the transition to post-quantum cryptography.