Post-Quantum Wallets: Kyber-768 vs SPHINCS+ Roles

By SynergyX · Published September 20, 2026 · Sources checked on this date

Key exchange vs signatures: what does each protect?

Imagine sending a confidential payment instruction. First, the recipient needs a way to read it without exposing it to an observer. Separately, the network needs to establish whether the person spending the funds authorized the transaction. Encryption addresses confidentiality; signatures address authorization and integrity.

This separation follows the roles in NIST FIPS 203 and FIPS 205. An encrypted connection to a node can coexist with a quantum-vulnerable transaction signature. Ask which message is protected, who verifies it, and which rule rejects an invalid spend.

Kyber-768 vs ML-KEM-768: related names, specific versions

CRYSTALS-Kyber is the KEM family selected through the NIST process. The final standard names the derived mechanism ML-KEM. SPHINCS+ is the signature family underlying SLH-DSA. A family name alone does not identify a particular standard revision, parameter set or interoperable implementation.

When reviewing a wallet, record the algorithm version and library version together. Confirm whether the software implements a Kyber submission version or final ML-KEM. For signatures, record the hash family, parameter set and encoding. Calling all of these variants interchangeable makes release reviews harder.

SYNX architecture: Kyber-768 and SPHINCS+-SHAKE-128s

SynergyX specifies Kyber-768 for key encapsulation and SPHINCS+-SHAKE-128s for signatures. Those are the project’s stated architecture and current signing parameter, confirmed for this guide. The SYNX technical whitepaper explains the product design; the wallet release page identifies the available builds.

The upstream SPHINCS+ parameter table lists 7,856-byte signatures, 32-byte public keys and 64-byte secret keys for its 128s parameter set. Application storage, containers and serialization may differ from those raw sizes. Matching a signature length is a useful consistency check, not proof that the algorithm is implemented correctly.

This is a project-authored architecture explanation, not an independent audit or a claim of NIST product certification. A strong implementation record ties the released binary to its signer, verifier, test vectors and consensus rules. Our post-quantum coin evaluation guide shows the evidence to request.

Five checks before choosing a post-quantum wallet

1. Name the asset and network. A wallet’s encryption feature does not change the validation rules of every coin it can display.
2. Trace spend authorization. Identify the signature checked for an actual transaction and whether any alternate authorization route still uses a vulnerable scheme.
3. Check malformed-message rejection. In a test environment, the verifier should reject a changed amount, recipient, signature or public key. A successful round trip alone is insufficient.
4. Connect the code to the release. Record the release identifier, binary digest, dependency versions and test-vector results. A whitepaper and a download link serve different evidentiary purposes.
5. Exercise recovery. A working signature does not help after a lost backup. Understand the stateful vs stateless backup distinction before funding a wallet.

Does a post-quantum wallet make Bitcoin quantum resistant?

A wallet feature cannot by itself replace the spending rules enforced by Bitcoin nodes. Evaluate the actual transaction path: native network authorization, smart-contract verification, custody and wrapped assets create different dependencies. For the original threat model, read the secp256k1 quantum resource estimates and the Bitcoin-holder wallet guide.