
15 Jul 2024 | Alan Lau | Director
Quantum Computing’s Impact on Cryptography
Quantum Computing’s Impact on Cryptography
Quantum computing, a revolutionary advancement in the realm of computation, has the potential to solve certain types of complex problems much faster than classical computers. One of the most significant areas where quantum computing is set to have a profound impact is cryptography. This blog delves into how quantum computing threatens current cryptographic technology and introduces readers to the emerging field of quantum-safe cryptography.
Understanding Cryptography
Cryptography is the method of securing communication through codes, ensuring that only the intended recipients can read the message. Modern cryptography relies on mathematical problems that are easy to solve in one direction but extremely difficult to reverse without a specific key. Two primary types of cryptographic algorithms are:
- Symmetric-key cryptography: The same key is used for both encryption and decryption.
- Asymmetric-key cryptography: A pair of keys (public and private) is used. The public key encrypts data, while the private key decrypts it.
The Quantum Threat
Quantum computers leverage the principles of quantum mechanics, using qubits to represent and process information in ways that classical bits cannot. This capability enables quantum computers to perform certain calculations exponentially faster. Two quantum algorithms pose a particular threat to current cryptographic systems:
- Shor’s Algorithm: Efficiently factors large numbers, undermining the security of widely used asymmetric cryptographic systems like RSA and ECC (Elliptic Curve Cryptography).
- Grover’s Algorithm: Provides a quadratic speedup for unstructured search problems, impacting symmetric-key cryptography by effectively halving the key length (e.g., a 128-bit key would offer only 64 bits of security).
Implications for Cryptography
The advent of quantum computers means that many cryptographic systems currently in use will become vulnerable. For instance:
- RSA and ECC: These will be easily broken by Shor’s algorithm, rendering secure communications, digital signatures, and key exchanges insecure.
- Symmetric-key algorithms: Though less affected, algorithms like AES will require longer keys to maintain security against Grover’s algorithm.
Towards Quantum-Safe Cryptography
To mitigate the risks posed by quantum computers, researchers are developing quantum-safe (or post-quantum) cryptographic algorithms. These algorithms are designed to be secure against both classical and quantum attacks. Some promising approaches include:
- Lattice-based cryptography: Relies on the hardness of lattice problems, which are believed to be resistant to quantum attacks.
- Code-based cryptography: Utilizes error-correcting codes to secure data, offering robustness against quantum threats.
- Multivariate polynomial cryptography: Based on the difficulty of solving systems of multivariate polynomial equations.
- Hash-based cryptography: Constructs digital signatures using hash functions, ensuring security against quantum adversaries.
The Road Ahead
The transition to quantum-safe cryptography is a complex and urgent task. It involves not only developing and standardizing new algorithms but also implementing them across various platforms and protocols. The National Institute of Standards and Technology (NIST) is actively working on standardizing post-quantum cryptographic algorithms, with a final selection expected in the near future.
Stay tuned for our next blog, where we will explore the current state of quantum-safe solutions in detail. We will discuss specific algorithms under consideration, their potential applications, and the steps you can take to prepare for a quantum-secure future.
References
- Books:
- Yanofsky, N.S., & Mannucci, M.A. (2008). Quantum Computing for Computer Scientists. Cambridge University Press.
- Bernstein, D.J., Buchmann, J., & Dahmen, E. (Eds.). (2009). Post-Quantum Cryptography. Springer.
- Websites and Articles:
- National Institute of Standards and Technology (NIST). (n.d.). Post-Quantum Cryptography. Retrieved from NIST PQC (https://csrc.nist.gov/projects/post-quantum-cryptography)
- IBM. (n.d.). Quantum Computing. Retrieved from IBM Quantum (https://www.ibm.com/quantum)
- Schneier, B. (2018). The Future of Cryptography: Post-Quantum Edition. Retrieved from Schneier on Security
- RSA Conference. (2020). Quantum Computing and Cryptography. Retrieved from RSA Conference
- Research Papers:
- Shor, P.W. (1994). “Algorithms for Quantum Computation: Discrete Logarithms and Factoring.” Proceedings 35th Annual Symposium on Foundations of Computer Science.
- Grover, L.K. (1996). “A Fast Quantum Mechanical Algorithm for Database Search.” Proceedings of the 28th Annual ACM Symposium on Theory of Computing.

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