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Key Encapsulation

NTRU

Number Theoretic Research Unit Cryptosystem

non-FIPSlattice-based2 parameter setsQNSP tier: default+provider: liboqsalso called: NTRU-HRSS, NTRU-HPS
One of the oldest lattice-based KEMs, in continuous study since 1996. NTRU was a NIST PQC finalist but not selected for FIPS standardisation in favour of ML-KEM.

Mechanism

How it works

NTRU operates over polynomial rings Z[x] / (x^n - 1) with small-coefficient polynomial inverses. Multiple parameter sets exist across NTRU-HPS and NTRU-HRSS variants.

Parameter Sets

2 variants shipped

Each variant trades security category against key, ciphertext, or signature size. QNSP exposes all variants via the @cuilabs/liboqs-native binding; tenant crypto-policy determines which are allowed.

VariantNIST LevelPublic KeySecret KeyCiphertextNote
ntru_hps2048509 / 677 / 821 / 1229L1699 B935 B699 B
ntru_hrss701 / 1373L31,138 B1,450 B1,138 B

NIST ACVP

Conformance evidence

QNSP runs the official NIST ACVP test vectors against every shipped algorithm. Live evidence + SHA-3-256 tamper digest at /verify/conformance.

@noble/post-quantum
non-addressable
Pure-JavaScript reference; cross-verification secondary on Maximum + Government tiers.
@cuilabs/liboqs-native
non-addressable
Native-C primary production engine. Runs across every QNSP backend service.
View live ACVP evidence →

Use Cases

When to use it

  • Migration from legacy NTRU deployments
  • Research and comparative analysis

Trade-offs

What you give up, what you get

  • Not on the NIST standardisation path — defer to ML-KEM for new deployments
  • 30+ years of cryptanalytic study

FAQ

NTRU — frequently asked questions

Concise, source-of-truth answers to the questions buyers and engineers ask most about this algorithm.

What is NTRU?

NTRU (Number Theoretic Research Unit Cryptosystem) is a lattice based post-quantum key encapsulation mechanism. It is designed to resist attacks from both classical and quantum computers, and QNSP ships 2 of its parameter sets. It is also known as NTRU-HRSS, NTRU-HPS.

Is NTRU NIST-standardized?

NTRU is not a finalized NIST FIPS standard. QNSP ships it as a non-FIPS post-quantum option, typically to add an independent cryptographic assumption (lattice based) alongside the FIPS-standardized ML-KEM and ML-DSA for defence-in-depth.

What is NTRU used for?

On QNSP, NTRU is used for Migration from legacy NTRU deployments; Research and comparative analysis. It is available from the default crypto-policy tier upward via the liboqs provider.

References

Primary sources