It's a race between Security and Crackers !

Quantum Computing is a game changer of this decade. But, one of the major downsides is their ability to crack classical cryptography in matter of minutes, if not in seconds, that puts the entire world at risk.

Imagine your cryptocurrency drained out because someone used the quantum computer to crack it wide open. Imagine the TLS layer (of HTTPS) for a Financial transaction is compromised in real time and the attacker gains access to your bank account. Imagine secure defence communications intercepted and decoded at the height of a conflict. What if confidential information is stored in encrypted form and decrypted later using Quantum computers?

Post-Quantum Cryptography (PQC) are algorithms designed to thwart attacks from quantum computers. The National Institute of Standards and Technology (NIST) has been leading an effort to standardize PQC algorithms. Some organisations have started preparing for the worst. (Read: https://thequantuminsider.com/2025/01/04/solana-takes-a-step-toward-pqc-era-with-quantum-resistant-vault/ )

Below are major PQC algorithms, along with a comparison and discussion of their resiliency.

Lattice-Based Cryptography

It is based on the hardness of problems like Learning with Errors (LWE) and Shortest Vector Problem (SVP) in high-dimensional lattices (of hundreds and thousands of dimensions). Though it has high resistance to quantum attacks its moderate resistance to side-channel attacks make it concerning an limits the applications.

• Examples: Kyber (key encapsulation mechanism), Dilithium (digital signatures), FrodoKEM, NTRU, SABER
• Advantages: Highly efficient (low computational cost and small key sizes in some cases). Strong theoretical foundations. Can be used for encryption, signatures, and even advanced tasks like secure computation.
• Challenges: Larger ciphertext sizes compared to classical cryptography.

Code-Based Cryptography

This relies on the difficulty of decoding randomly generated linear codes (e.g., Goppa codes). Though it has excellent quantum resistance, it is highly vulnerable to classical side-channel attacks if not implemented carefully. Going by the history of cryptographic implementations, one can expect many CVRs raised on this.

• Examples: Classic McEliece
• Advantages: Extremely strong theoretical basis. Proven security for very long time.
• Challenges: Very large public key sizes, limiting practicality.

Multivariate Quadratic (MQ) Equations

Solving systems of m multivariate quadratic equations in n variables (MQ-problem) over finite fields is NP-hard problem. The MQ equation driven security is based on solving systems of multivariate quadratic equations over finite fields. This set of PQC algorithms is generally weaker against quantum attacks compared to lattice and code-based systems.

• Examples: Rainbow, GeMSS
• Advantages:Efficient for small-scale systems.
• Challenges:Some schemes (like Rainbow) have been recently broken.

Hash-Based Cryptography

Traditional cryptographic Hash based approaches offer tremendous avenues in PQC. Though it offers very high quantum and classical security, concerns remain about the long term viability of maintaining large signature sizes.

• Examples: SPHINCS+, LMS (Leighton-Micali Signature Scheme)
• Advantages: Simple and highly secure if the underlying hash function is secure. Stateless variants (like SPHINCS+) address usability concerns.
• Challenges: Large signature sizes.

Isogeny-Based Cryptography

These algorithms leverage the difficulty of computing isogenies between supersingular elliptic curves. It offers moderate quantum resistance but further research needed after recent cryptanalytic breakthroughs.

• Examples: SIKE (Supersingular Isogeny Key Encapsulation), SIDH, CSIDH
• Advantages:Extremely small key sizes as compared to other PQC algorithms.
• Challenges:Computationally intensive.SIKE was recently broken in some parameter sets.

Symmetric-Key Quantum-Resistant Algorithms

These algorithms leverage Grover's algorithm's quadratic speedup and is able to provide security by using larger key sizes. This allows it to be resistant to Grover's algorithm, provided the key size is doubled.

• Examples: AES-256, SHA-3
• Advantages:Well-understood and efficient.
• Challenges:Limited to symmetric-key contexts

Current Status

• NIST's PQC standardization effort is in its final stages (as of 2025).
• Kyber (encryption) and Dilithium (signatures) are the leading candidates for standardization due to their strong performance and security properties.
• Other algorithms (e.g., Classic McEliece and SPHINCS+) are also under consideration for specific use cases.

Conclusion

Extensive research investment is needed to ensure a reliable PQC is established. Expect plenty of new algorithms being attempted (and discarded) in next few years. This is akin to early days of classical cryptography.

#quantumComputing #postQuantumCryptography #informationsecurity #infosec #quantumComputer #cryptography #computing #QuantumTech #QuantumSupremacy #PQC #QuantumEncryption #QuantumProof #CyberResilience #QuantumSecurity #QuantumSafe #QuantumAlgorithms #QuantumFuture #QuantumMechanics