kali-decoder Midnight Consensus
The Midnight Network uses a modified Substrate consensus stack: AURA for block production and GRANDPA for finality. Both are extended for Midnight as a Cardano Partnerchain.
Architecture overview
flowchart TB
subgraph Selection["Validator selection"]
SPO["Cardano SPO stake delegation"]
Perm["Optional permissioned validators"]
VS["Custom validator set function"]
SPO --> VS
Perm --> VS
end
subgraph Production["Block production — AURA"]
VS --> Slots["Round-robin slots + session keys"]
Slots --> Block["New block proposed"]
end
subgraph Finality["Finality — GRANDPA"]
Block --> Votes["Validator votes on chain"]
Votes --> Final["Provable finality"]
end
Validator selection
Unlike standard Substrate chains, Midnight uses a custom validator set selection function that:
- Accounts for stake delegation from Cardano Stake Pool Operators (SPOs), letting existing Cardano validators participate in Midnight consensus.
- Supports optional permissioned validators for hybrid public/private network deployments.
| Model | Role |
|---|---|
| SPO delegation | Bridges Cardano stake into Partnerchain validator eligibility |
| Permissioned set | Adds known operators for regulated or consortium networks |
| Custom selection | Combines both into the active session validator set |
AURA: Block production
AURA (Authority Round) is a proof-of-authority (PoA) algorithm that determines which validator produces each block.
- Validators take turns in round-robin order.
- Scheduling uses predefined slots and session keys.
- Properties: simple, fast, deterministic — suited to high-throughput chains with known validator sets.
AURA is not Midnight-specific; it originated in OpenEthereum. See the Polkadot protocol glossary — AURA.
sequenceDiagram
participant V1 as Validator 1
participant V2 as Validator 2
participant V3 as Validator 3
participant Chain as Chain
Note over V1,V3: Slot N — Validator 1's turn
V1->>Chain: Produce block N
Note over V1,V3: Slot N+1 — Validator 2's turn
V2->>Chain: Produce block N+1
Note over V1,V3: Slot N+2 — Validator 3's turn
V3->>Chain: Produce block N+2
Signing: Block authorship messages in AURA are signed with sr25519 (see the Cryptography skill).
GRANDPA: Finality
GRANDPA (GHOST-based Recursive ANcestor Deriving Prefix Agreement) provides asynchronous, provable finality.
- Operates independently of block production.
- Validators vote on chains; blocks finalize when they receive sufficient support.
- General-purpose Polkadot component — formal specification and Polkadot glossary.
flowchart LR
A["Blocks produced (AURA)"] --> B["GRANDPA voters observe chain"]
B --> C{"≥ threshold support?"}
C -->|Yes| D["Block finalized — irreversible"]
C -->|No| E["Remains unfinalized / fork possible"]
Signing: GRANDPA finality messages use Ed25519.
How AURA and GRANDPA work together
| Layer | Responsibility | Midnight extension |
|---|---|---|
| AURA | Who builds the next block | Standard PoA over Partnerchain validator set |
| GRANDPA | Which blocks are final | Standard async finality gadget |
| Validator set | Who may participate | SPO delegation + optional permissioned operators |
Key insight: Block production can continue while GRANDPA finalizes earlier blocks asynchronously — throughput and safety are decoupled.
Related skills
midnight-cryptography/— signature schemes used by AURA and GRANDPAmidnight-onchain-logic/— runtime pallets (pallet-aura,pallet-grandpa, session management)midnight-p2p-networking/— how validators discover and communicate