Resources

PQC & cybersecurity glossary

Clear definitions of the terms that matter in the transition to quantum-safe security.

A

AES-256: Symmetric block cipher with a 256-bit key. Considered quantum-resistant because Grover's algorithm only halves effective key strength.
Attestation: Cryptographic proof, typically from a TPM, that a device booted a known, unmodified chain of software.

CBOM: Cryptographic Bill of Materials: a machine-readable inventory of the algorithms, keys, certificates and libraries a system uses. Supported in CycloneDX.
CNSA 2.0: The NSA's Commercial National Security Algorithm Suite 2.0, specifying quantum-resistant algorithms and transition deadlines for national security systems.
CRQC: Cryptographically Relevant Quantum Computer: a quantum computer powerful enough to break RSA and elliptic-curve cryptography.
Crypto-agility: The ability to replace cryptographic algorithms in a system without significant redesign.

ECDH / ECDSA: Elliptic-curve Diffie-Hellman key agreement and elliptic-curve digital signatures. Both are broken by Shor's algorithm.

FIPS 203 / 204 / 205: NIST's post-quantum standards for ML-KEM, ML-DSA and SLH-DSA, published in August 2024.
Forward secrecy: Property where compromise of long-term keys does not expose past session keys, achieved with ephemeral key exchange.

Grover's algorithm: Quantum search algorithm giving a quadratic speed-up against symmetric keys and hashes; mitigated by doubling key sizes.

Harvest now, decrypt later: Attack strategy of recording encrypted data today to decrypt once a CRQC exists.
HKDF: HMAC-based Key Derivation Function, used to combine classical and post-quantum shared secrets in hybrid key exchange.
Hybrid key exchange: Combining a classical and a post-quantum key exchange so the result stays secure if either one holds.

KEM: Key Encapsulation Mechanism: a public-key primitive that securely transports a randomly generated shared secret.

Lattice-based cryptography: Cryptography based on hard problems over mathematical lattices, such as Module-LWE. It is the basis of ML-KEM and ML-DSA.
LMS / XMSS: Stateful hash-based signature schemes standardised in NIST SP 800-208, recommended for firmware signing.

Measured boot: Recording a hash of each boot component into TPM PCRs so the boot sequence can later be verified.
ML-DSA: Module-Lattice-Based Digital Signature Algorithm (FIPS 204), formerly CRYSTALS-Dilithium.
ML-KEM: Module-Lattice-Based Key-Encapsulation Mechanism (FIPS 203), formerly CRYSTALS-Kyber.
Mosca's inequality: Risk rule x + y > z: if data shelf-life plus migration time exceeds time to a CRQC, data is at risk.

PCR: Platform Configuration Register: a TPM register that accumulates boot measurements via hash extension.
PQC: Post-Quantum Cryptography: classical algorithms designed to resist attacks by quantum computers.

Q-Day: The point at which a CRQC can break widely deployed public-key cryptography.
QKD: Quantum Key Distribution: exchanging keys using quantum physics over dedicated optical links. Distinct from PQC.
QRNG: Quantum Random Number Generator: an entropy source based on quantum physical processes.

Shor's algorithm: Quantum algorithm that efficiently factors integers and computes discrete logarithms, breaking RSA, DH and ECC.
SLH-DSA: Stateless Hash-Based Digital Signature Algorithm (FIPS 205), formerly SPHINCS+.

TPM 2.0: Trusted Platform Module: a hardware security chip providing key storage, measured boot and attestation.

X25519MLKEM768: Hybrid TLS 1.3 key exchange group combining X25519 with ML-KEM-768.

Zero Trust: Security model (NIST SP 800-207) where no user, device or network is trusted by default; every access is verified.

Book a technical briefing or a QScan readiness assessment with our engineers.