j4flmao Post-Quantum Cryptography (PQC)
1. Skill Context
Focus: Securing software systems against the future threat of Cryptographically Relevant Quantum Computers (CRQCs) that can break modern asymmetric encryption. Triggers: post-quantum, pqc, lattice-based, kyber, dilithium, nist-pqc, quantum-resistant.
2. The Quantum Threat (Q-Day)
Currently, all secure web traffic (HTTPS/TLS), digital signatures, and cryptocurrency wallets rely on asymmetric cryptography (RSA, ECC/ECDSA). These algorithms assume that prime factorization and discrete logarithms are impossibly slow to solve on classical computers. A sufficiently large quantum computer running Shor's Algorithm will solve these problems in hours, instantly decrypting global internet traffic. This hypothetical date is referred to as "Q-Day".
"Store Now, Decrypt Later" (SNDL): Adversaries are currently scraping and storing vast amounts of encrypted internet traffic. When Q-Day arrives, they will decrypt this historical data. Hence, PQC transition must happen now, not when Q-Day arrives.
3. NIST PQC Standards (2024+)
The US National Institute of Standards and Technology (NIST) has standardized new algorithms that rely on math problems (e.g., Lattices) which are hard for both classical and quantum computers.
A. Key Encapsulation Mechanism (KEM)
Used for establishing secure shared secrets over an insecure channel (replacing RSA Key Exchange and Elliptic Curve Diffie-Hellman - ECDH).
- Standard:
ML-KEM(Module-Lattice-Based Key-Encapsulation Mechanism), originally known as Kyber.
B. Digital Signatures
Used for authenticating identities and signing documents/code (replacing RSA Signatures and ECDSA).
- Standard 1:
ML-DSA(Module-Lattice-Based Digital Signature Algorithm), originally known as Dilithium. - Standard 2:
SLH-DSA(Stateless Hash-Based Digital Signature Algorithm), originally known as SPHINCS+. - Standard 3:
FN-DSA(FFT over NTRU-Lattice-Based Digital Signature Algorithm), originally known as FALCON.
4. Implementation Strategy (Hybrid Mode)
Because PQC algorithms are relatively new, they have not withstood 30 years of mathematical scrutiny like RSA. Implementing pure PQC in production is currently considered risky.
- The Standard Approach: Use Hybrid Cryptography. Combine a classical algorithm (e.g., X25519) with a PQC algorithm (e.g., ML-KEM). The session is secure as long as at least one of the underlying algorithms remains unbroken.
5. Symmetric Crypto is Quantum-Resistant
Quantum computers (via Grover's Algorithm) effectively halve the bit-strength of symmetric encryption.
- AES-128: Becomes equivalent to 64-bit security (Vulnerable).
- AES-256: Becomes equivalent to 128-bit security (Safe).
- Action: Simply double your symmetric key sizes. AES-256 and SHA-256/SHA-3 are considered post-quantum secure.