🔍 1. Overview

Cardano uses staking certificates to manage the lifecycle of stake keys and their association with stake pools. These certificates are CBOR-encoded structures embedded in the transaction body metadata.

Three main certificate types:

1. stake_key_registration_certificate Registers a stake key on-chain so it can participate in delegation or staking rewards.
2. stake_delegation_certificate Delegates the registered stake key to a specific stake pool.
3. stake_deregistration_certificate Deregisters a stake key from the ledger, which effectively ceases its staking capabilities and may refund the deposit.

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🔧 2. Sample: Generating a Delegation Certificate

cardano-cli stake-address delegation-certificate \
  --stake-verification-key-file stake.vkey \
  --cold-verification-key-file pool.vkey \
  --out-file delegation.cert

This generates a CBOR-encoded file (delegation.cert) containing:

• The hash of the stake key (derived from stake.vkey)
• The pool ID (hash of the pool’s cold key from pool.vkey)
• The network ID (mainnet/testnet identifier)

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📦 3. CBOR Serialization Format

Internally, the certificate is serialized according to Cardano’s CBOR format, as specified in Cardano Ledger specifications (Shelley Era).

For a stake delegation certificate, the CBOR structure is typically:

[
  2,                             // Certificate type: Delegation
  [
    0,                           // Credential type: KeyHash (as opposed to ScriptHash)
    <28-byte Stake Key Hash>     // Hash of the stake verification key
  ],
  <28-byte Pool Key Hash>        // Pool ID (cold key hash)
]

For reference:

Certificate Type	CBOR Tag
stake key registration	0
stake key deregistration	1
stake delegation	2

Each of these structures is embedded in the transaction body, which itself is CBOR-encoded and includes:

• Inputs
• Outputs
• Fee
• TTL (time-to-live)
• [Certificates] (array of staking certificates)
• Withdrawals (optional)
• Auxiliary data hash (optional)

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🛠️ 4. Important Metadata Fields in Delegation Certificate

Field	Description
Stake Key Hash	28-byte Blake2b-224 hash of the stake key
Pool ID	28-byte Blake2b-224 hash of the pool’s cold key
Network ID	Distinguishes mainnet (1) from testnet (0)

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⚠️ 5. Additional Notes:

• cardano-cli abstracts the complexity of generating this CBOR structure.
• When submitting a transaction with this certificate, the transaction must also be signed by the corresponding stake key (for proof of ownership) and by the payment key funding the transaction (to pay fees).
• These certificates are essential for controlling staking rights and rewards without transferring ADA.

Here’s a real example showing how to generate a stake delegation certificate, then inspect and decode its CBOR structure manually to understand what’s inside.