Midnight Concepts

Comprehensive guide to Midnight Network's foundational concepts, privacy technology, and architecture.

What is Midnight?

Midnight is a zero-knowledge partner chain to Cardano that enables privacy-preserving blockchain applications. It solves the fundamental tension between transparency and privacy in blockchain technology through advanced zero-knowledge cryptography.

Key Innovation: Selective disclosure - applications can choose exactly what information to make public and what to keep private, while maintaining verifiability.

Core Features:

• Privacy-preserving smart contracts
• Selective disclosure
• UTXO + Account hybrid model
• Zswap for private token transfers
• Integration with Cardano security

Architecture Overview

Three-Part Contract Structure

Each Compact smart contract has three components:

1. Replicated Component (Public Ledger)

   • Stored on-chain
   • Verifiable by anyone
   • Contains public state

2. Zero-Knowledge Circuit

   • Proves correct execution
   • Keeps inputs private
   • Generates proofs

3. Local Component (Off-chain)

   • Runs in DApp
   • Arbitrary computation
   • Witness functions

Core Concepts

1. Kachina Protocol

THE foundational smart contract architecture that enables private state management.

How It Works:

1. User has private state (witness)
2. Circuit proves valid transition
3. Public state updates on-chain
4. Both states stay consistent

Key Properties:

• Public state + Private state model
• Zero-knowledge proof bridge
• Transcript-based concurrency
• Universally Composable (UC) security

From the whitepaper: Kachina uses a novel combination of a public ledger and private witnesses, with circuits proving correct state transitions.

2. Privacy Mechanisms

Zswap Protocol

Privacy-preserving token system hiding:

• Transaction amounts
• Sender/recipient identities
• Token types

Features:

• Shielded tokens (hidden)
• Unshielded tokens (public)
• Conversion between both
• Zero-knowledge proofs for validity

// Shielded transfer flow
1. Create input from owned shielded coin
2. Create output for recipient
3. Generate ZK proof
4. Submit to network
5. Recipient can receive and spend

Selective Disclosure

Applications control exactly what data is public vs private:

// Private comparison
export circuit verifyAge(age: Uint<32>): Boolean {
  const secretAge = witness Age();  // Private
  return disclose(secretAge >= 18);  // Only reveal boolean
}

3. Ledger Models

Midnight uses a hybrid UTXO + Account model:

UTXO Model (Ledger Tokens)

• Like Bitcoin
• Each coin spent exactly once
• Good for: privacy, parallelism

Account Model (Contract Tokens)

• Like Ethereum
• Mutable stored state
• Good for: complex contracts

Decision Matrix:

Use Case	Recommended Model
Simple transfers	UTXO
Token balances	Account
Complex state	Account
High privacy	UTXO
High throughput	UTXO
Smart contracts	Account

4. Zero-Knowledge Proofs

Mathematical techniques proving computations are correct without revealing inputs.

Key Concepts:

• Circuit: Compiled from Compact code
• Witness: Private inputs
• Public inputs: Transparent arguments
• Proof: Succinct verification

Use in Midnight:

• Valid state transitions
• Transaction validity
• Credential verification

5. Partner Chain Architecture

Midnight is a partner chain to Cardano:

Benefits:

• Inherits Cardano security
• EUTxO model
• proven consensus
• Decentralized infrastructure

Integration:

• Consensus via Cardano
• State checkpointing
• Token bridging

Privacy Model

What Can Be Private

Data	Privacy Level	Disclosure
Account balances	Optional	User choice
Transaction amounts	Optional	Hidden in Zswap
Identities	Optional	Hidden in Zswap
Business logic	Automatic	Circuit keeps secret
Credentials	Selective	Only proven facts

What Is Always Public

• Transaction existence
• Block order
• State updates (not values)
• Contract code

Use Cases by Category

Finance & DeFi

1. Confidential Trading

   • Hidden amounts
   • Hidden positions
   • See: LunarSwap

2. Private Lending

   • Hidden collateral
   • Hidden debt
   • Credit scoring proof only

3. Liquid Staking

   • Hydra Stake
   • Privacy-preserving rewards
   • LST functionality

4. Stablecoins

   • Statera Protocol
   • Over-collateralized
   • Privacy features

Identity & Privacy

1. ZK Identity

   • Midnames - ZK DID
   • Selective attribute disclosure

2. KYC Attestations

   • KYC Midnight
   • Prove without revealing data

3. Private Credentials

   • Midnight Cloak
   • Age/residence verification

4. RWA Trading

   • Real World Assets
   • Privacy-first tokenization

Governance

1. Private Voting

   • Secret ballots
   • Verifiable counting
   • No vote selling

2. Crowdfunding

   • FundAGoal
   • Anonymous contributions

Gaming

1. On-chain Gaming

   • Midnight Starship
   • ZK leaderboards
   • Privacy-first gaming

2. Verifiable RNG

   • Dice Roll
   • Fair randomness

Tokenomics

Native Token: NIGHT

• Used for fees
• Staking rewards
• Governance
• Unit: 1 NIGHT = 10^6 Stars

DUST: Dynamic Gas System

DUST is NOT a static balance. It's a dynamic gas system where your DUST balance changes based on your NIGHT holdings and time.

Analogy:

• NIGHT = Solar Panel (valuable asset you hold)
• DUST = Electricity (generated from the Solar Panel)
• Usage = Consuming electricity to power operations

How DUST Works

1. Registration: Link your NIGHT address to a DUST public key via the Registration Table
2. Generation Phase: DUST grows linearly from creation until it hits a cap (ρ)
3. Constant Phase: Stays at maximum value
4. Decay Phase: Once NIGHT is spent, DUST decays to zero
5. Zero Phase: No more gas available

Key Properties

Property	Description
Shielded	DUST UTXOs are private
Non-transferable	Cannot send DUST to others
Dynamic	Value changes over time
Derived	Computed from NIGHT UTXO

DUST Units

• DUST unit: 1 DUST = 10^15 Specks
• Initial ratio: ~5 DUST per NIGHT
• Grace period: ~3 hours (for transaction timestamp)

Spending Rules

• DUST can be spent multiple times
• New UTXO always created, even with zero value
• Decay continues even during spending
• Partial NIGHT spend creates fresh DUST generation

Full Architecture

The full technical specification is available in the DUST spec.

Programmatic DUST Generation (Preprod)

On Preprod network, DUST is no longer available from the faucet. DApps must programmatically generate DUST:

1. Fund wallet: Get tNIGHT from Preprod faucet
2. Designate dust address: Register your unshielded address to a dust address
3. Generate DUST: Your tNIGHT holdings automatically generate DUST for gas fees

Reference: midnight-dust-generator - Official script for Preprod

Prerequisites:

• Node.js v18+
• Docker Desktop (for proof server on port 6300)

npm install
docker compose -f proof-server.yml up  # terminal 1
npm start  # terminal 2 - interactive walkthrough

The script handles: wallet creation/restoration, funding detection, address designation, and registration.

Dust: Anonymous Tokens (Legacy)

• Privacy coins
• Unlinkable
• Denominations (1, 10, 100, etc.)

Security Model

Consensus

• Inherited from Cardano
• Proof of Stake
• BFT-style finality

Privacy Guarantees

What Midnight provides:

• Computational privacy (ZK circuits)
• Transaction unlinkability (Zswap)
• Selective disclosure

What Midnight does NOT provide:

• Metadata privacy (timing, size)
• Network-level privacy
• Quantum resistance (future)

When to Use Midnight

✅ Best Fit For

• Private DeFi - Confidential trading, lending
• Identity - KYC, credentials, age proof
• Voting - Private ballots, governance
• RWA - Privacy-first asset tokenization
• Gaming - Verifiable RNG, ZK leaderboards

❌ Not Ideal For

• Fully public applications (use Cardano directly)
• High-throughput needs (consider Hydra)
• Simple transfers (Cardano tx is sufficient)

Technical Deep Dives

ZK Circuit Flow

pragma language_version >= 0.20;

// Public state
export ledger balance: Uint<64>;

// Private witness  
witness secretAmount(): Uint<64>;

// Circuit enforces rules
export circuit deposit(amount: Uint<64>): [] {
  // Verify private input
  const secret = secretAmount();
  
  // Only disclose commitment
  const commitment = disclose(persistentCommit(balance.read(), secret));
  
  // Update public
  balance.write(balance.read() + amount);
}

Zswap Flow

1. Shield coins exist locally
2. Create input referencing coin
3. Generate proof (ownership, sufficient amount)
4. Create outputs (recipient + change)
5. Submit to network
6. Recipients can spend in future

State Consistency

Kachina Guarantees:

1. If circuit proves valid → state updates
2. If circuit fails → no state change
3. Private state stays private
4. Public verification always possible

Midnight Improvement Proposals (MIPs)

Formal process for proposing changes to Midnight: midnight-improvement-proposals

Process

1. Idea → 2. Draft → 3. Submit PR → 4. Review → 5. Accepted → 6. Implemented → 7. Deployed

Categories

Category	Description
Core	Protocol, consensus, VM changes
Standards	Smart contract interfaces, data formats
Networking	P2P communication
Governance	Decision-making processes
Informational	Guidelines, research (no change)

Statuses

Proposed → Review → Accepted → Implemented → Superseded/Obsolete/Rejected/Withdrawn

MIP Template

---
MIP: <number>
Title: <title>
Authors: <name> <github>
Status: Proposed
Category: <Core|Standards|Networking|Governance|Informational>
Created: <date>
Requires: <other MIPs>
Replaces: <MIP number>
---

Reference: MIP-1: MIP Process

Glossary

Term	Definition
Circuit	ZK program proving computation
Witness	Private input to circuit
Transcript	Ordered transaction history
Zswap	Private token system
Selective Disclosure	Explicit privacy control
Partner Chain	Secondary chain to Cardano
Compact	ZK smart contract language
Shielded	Privacy-preserving transaction
UTXO	Unspent Transaction Output
DUST	Privacy coin denominations

Learn More

Official Resources

• Midnight Docs
• Kachina Paper
• Developer Academy
• Community Forum

Awesome DApps (Reference Implementations)

• midnight-awesome-dapps
• OpenZeppelin Contracts

Discord Community

• Midnight Network Discord

Social

• X/Twitter
• YouTube