ReddRadar
Agent skill
privacy-patterns
Implement privacy-preserving patterns using zero-knowledge proofs on Midnight Network. Use when designing private data handling, commitment schemes, nullifiers, or selective disclosure. Triggers on privacy, ZK proof, commitment, nullifier, or confidential computing questions.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/development/privacy-patterns-fractionestate-midnight-dev-skills
SKILL.md
Privacy Patterns for Midnight
Design and implement privacy-preserving applications using zero-knowledge proofs.
Core Privacy Model
| Concept | Description | Visibility |
|---|---|---|
| Public | Ledger state | Everyone |
| Private | Circuit inputs | Only prover |
| Witness | Prover-provided data | Only prover |
| Disclosed | Explicitly revealed | Everyone |
Reference Files
| Topic | Resource |
|---|---|
| Zero-Knowledge Basics | references/zk-fundamentals.md |
| Commitment Schemes | references/commitments.md |
| Nullifier Patterns | references/nullifiers.md |
| Selective Disclosure | references/selective-disclosure.md |
Pattern Overview
1. Commitment Scheme
Hide a value while binding to it:
commitment = persistentCommit(value, randomness);
// Later: prove you know the opening
2. Nullifier Pattern
Prevent double-use without revealing identity:
nullifier = transientHash(secret, commitment);
// Can only be generated once per commitment
3. Selective Disclosure
Prove properties without revealing data:
// Prove over 18 without revealing actual age
disclose(age >= 18); // Only boolean is public
4. Merkle Membership
Prove membership in a set without revealing position:
// Verify path from leaf to root
assert verifyMerklePath(leaf, proof, root);
Quick Examples
Private Balance Check
// Only reveal if balance is sufficient, not actual amount
export circuit checkFunds(balance: Uint<64>, required: Uint<64>): Boolean {
return disclose(balance >= required);
}
Anonymous Voting
export circuit vote(voter: Bytes<32>, choice: Boolean): [] {
// Voter identity disclosed (prevents double voting)
hasVoted.insert(voter);
// Choice remains private, only totals change
if (choice) { yesCount = yesCount + 1; }
}
Commitment-Reveal
witness randomness: Field;
// Phase 1: Commit
export circuit commit(value: Uint<64>): Field {
return persistentCommit(value, randomness);
}
// Phase 2: Reveal
export circuit reveal(value: Uint<64>, commitment: Field): [] {
assert persistentCommit(value, randomness) == commitment;
disclose(value);
}
Privacy Best Practices
- ✅ Use
witnessfor data that should never appear on-chain - ✅ Use
persistentCommit(with randomness) to hide values - ✅ Use nullifiers to prevent double-actions
- ✅ Disclose only what's necessary (prefer booleans)
- ❌ Don't store unhashed sensitive data on ledger
- ❌ Don't use predictable randomness in commitments
- ❌ Don't reveal intermediate values unnecessarily
Privacy Levels
┌────────────────────────────────────────────────┐
│ Level 0: Fully Public │
│ - All data visible on-chain │
├────────────────────────────────────────────────┤
│ Level 1: Hidden Values │
│ - Commitments on-chain, values private │
├────────────────────────────────────────────────┤
│ Level 2: Unlinkable Actions │
│ - Nullifiers prevent linking actions │
├────────────────────────────────────────────────┤
│ Level 3: Anonymous Membership │
│ - Merkle proofs hide set position │
└────────────────────────────────────────────────┘
When to Use Each Pattern
| Pattern | Use Case |
|---|---|
| Commitment | Sealed bids, hidden votes before reveal |
| Nullifier | Preventing double-spend, one-time tokens |
| Merkle Proof | Membership in allowlist without revealing identity |
| Selective Disclosure | Age verification, credential proofs |
Resources
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