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Digital Signature

CROSS

Codes and Restricted Objects Signature Scheme

non-FIPScode-based1 parameter setsQNSP tier: default+provider: liboqs
Code-based signature using the MPC-in-the-head paradigm over restricted syndrome decoding. NIST PQC additional-signatures track candidate.

Mechanism

How it works

CROSS combines syndrome decoding with the MPC-in-the-head zero-knowledge proof system to produce signatures whose security reduces to the hardness of decoding random codes. Multiple parameter sets balance signature size against signing speed.

Parameter Sets

1 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 KeySignatureNote
CROSS-RSDP / CROSS-RSDPG (multiple param sets)L577 B32 B13,152 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

  • Code-based signature option for assumption diversification
  • NIST PQC additional-signatures track inclusion

Trade-offs

What you give up, what you get

  • Tiny public keys (77 bytes), large signatures
  • Code-based assumption diversifies away from lattice-based signature dominance

FAQ

CROSS — frequently asked questions

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

What is CROSS?

CROSS (Codes and Restricted Objects Signature Scheme) is a code based post-quantum digital signature scheme. It is designed to resist attacks from both classical and quantum computers, and QNSP ships 1 of its parameter sets.

Is CROSS NIST-standardized?

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

What is CROSS used for?

On QNSP, CROSS is used for Code-based signature option for assumption diversification; NIST PQC additional-signatures track inclusion. It is available from the default crypto-policy tier upward via the liboqs provider.

References

Primary sources