Zcash zk-SNARKs: Groth16, Halo 2 and Quantum Risk
Sapling and Orchard use different proof systems. Updated .
What are Zcash zk-SNARKs?
Zcash uses zero-knowledge proofs to validate shielded transactions without publishing all the transaction details. Sapling uses Groth16; Orchard uses Halo 2. The Electric Coin Company release notes explicitly distinguish the two proof systems and their validation paths.
Halo 2 rend-il le Zcash résistant aux quantiques ?
Removing a trusted setup and achieving post-quantum security are different goals. The NU5 release introduced Orchard and Halo to remove reliance on setup ceremonies. That change does not by itself replace the elliptic-curve assumptions used by the proof and spending systems.
Read the full Zcash quantum-resistance analysis for the distinction between proof soundness, spending authority and privacy. Soundness asks whether invalid statements can be accepted. Spending authority asks who can authorize funds. Privacy asks what an observer can learn. Those are separate claims to evaluate.
For comparison, see Monero quantum resistance et Bitcoin secp256k1 attack-resource estimates. Resource counts for one curve are not automatically counts for another.
🔬 La réalité technique
| Composant Zcash | Primitive cryptographique | Vulnérabilité quantique |
|---|---|---|
| zk-SNARK (Groth16) | Appariements BLS12-381 | Vulnerable to a sufficiently capable quantum attacker |
| Protocole de jeune arbre | Courbe de Jujub | Vulnerable to a sufficiently capable quantum attacker |
| Protocole du verger | Courbes Pallas/Vesta | Vulnerable to a sufficiently capable quantum attacker |
| Signatures RedJubjub | Schnorr sur CE | Vulnerable to a sufficiently capable quantum attacker |
🎯 Le scénario d'attaque
Étape 1 : L'ordinateur quantique exécute l'algorithme de Shor sur BLS12-381
Related reading: Le Zcash est-il résistant quantique en 2026 ? Analyse critique.
Étape 2 : The targeted elliptic-curve discrete logarithm becomes tractable on that sufficiently capable machine
Étape 3 : Assess the affected proof, signature and key-agreement components separately
Étape 4 : Determine historical privacy exposure from the protocol and data available to the attacker
⚠️ Le verger ne vous sauve pas
Malgré les affirmations marketing, Orchard utilise des courbes de Pallas, toujours des courbes elliptiques, toujours vulnérables quantiquement.
✅ Alternative sûre quantique
SynX offre une véritable sécurité post-quantique sans cryptographie à courbe elliptique vulnérable :
- Kyber-768 : Encapsulation de clé basée sur un treillis (NIST FIPS 203)
- SPHINCS+-SHAKE-128s : Signatures basées sur le hachage (NIST FIPS 205)
Zcash zk-SNARKs: common questions
Are Zcash zk-SNARKs quantum resistant?
Zcash uses Groth16 for Sapling and Halo 2 for Orchard. These systems depend on elliptic-curve assumptions; removing a trusted setup does not establish post-quantum security.
Will Zcash shielded transactions remain private against quantum?
Proof soundness, spending authorization and note confidentiality are separate properties. A quantum attack against one does not by itself demonstrate recovery of every historical transaction.
Can quantum computers break zero-knowledge proofs?
Quantum resistance depends on the proof system and its assumptions. Zero knowledge alone does not mean post-quantum security; different constructions have different threat models.