Cardano Improvement Proposals


CIP 36 - Catalyst/Voltaire Registration Transaction Metadata Format (Updated)

Contents

Abstract

Cardano uses a sidechain for its treasury system. One needs to "register" to participate on this sidechain by submitting a registration transaction on the mainnet chain. This CIP details the registration transaction format. This is a revised version of the original CIP-15.

Motivation

Cardano uses a sidechain for its treasury system ("Catalyst") and for other voting purposes. One of the desirable properties of this sidechain is that even if its safety is compromised, it doesn't cause loss of funds on the main Cardano chain. To achieve this, instead of using your wallet's recovery phrase on the sidechain, we need to use a brand new "voting key".

However, since 1 ADA = 1 vote, a user needs to associate their mainnet ADA to their new voting key. This can be achieved through a registration transaction.

In addition, to encourage participation by a broader range of ADA holders, it should be possible to delegate one's rights to vote to (possibly multiple) representatives and/or expert voters. Such delegations will still be able to receive Catalyst rewards.

We therefore need a registration transaction that serves three purposes:

  1. Registers a "voting key" to be included in the sidechain and/or delegates to existing "voting key"s
  2. Associates mainnet ADA to this voting key(s)
  3. Declares an address to receive Catalyst rewards

Note: This schema does not attempt to differentiate delegations from direct registrations, as the two options have exactly the same format. It also does not distinguish between delegations that are made as "private" arrangements (proxy votes) from those that are made by delegating to representatives who promote themselves publicly. Distinguishing these possibilities is left to upper layers or future revisions of this standard, if required. In this document, we will use the term 'delegations' to refer to all these possibilities.

Specification

Registration metadata format

A registration transaction is a regular Cardano transaction with a specific transaction metadata associated with it.

Notably, there should be five entries inside the metadata map:

Delegation format

A delegation assigns (a portion of) the ADA controlled by one or more UTxOs on mainnet to the voting key in the sidechain as voting power. The UTxOs can be identified via the stake address at some designated point in time.

Each delegation therefore contains:

Voting key derivation path

To avoid linking voting keys directly with Cardano spending keys, the voting key derivation path must start with a specific segment:

m / 1694' / 1815' / account' / chain / address_index

Associating voting power with a voting key

This method has been used since Fund 2. For future fund iterations, a new method making use of time-lock scripts may be introduced as described below.

Recall: Cardano uses the UTXO model so to completely associate a wallet's balance with a voting key (i.e. including enterprise addresses), we would need to associate every payment key to a voting key individually. Although there are attempts at this (see CIP-0008), the resulting data structure is a little excessive for on-chain metadata (which we want to keep small)

Given the above, we choose to associate staking credentials with voting keys. At the moment, the only supported staking credential is a staking key. Since most Cardano wallets only use base addresses for Shelley wallet types, in most cases this should perfectly match the user's wallet.

The voting power that is associated with each delegated voting key is derived from the user's total voting power as follows.

  1. The total weight is calculated as a sum of all the weights;
  2. The user's total voting power is calculated as a whole number of ADA (rounded down);
  3. The voting power associated with each voting key in the delegation array is calculated as the weighted fraction of the total voting power (rounded down);
  4. Any remaining voting power is assigned to the last voting key in the delegation array.

This ensures that the voter's total voting power is never accidentally reduced through poor choices of weights, and that all voting powers are exact ADA.

Example

Voting registration example:

61284: {
      // delegations - CBOR byte array 
      1: [["0xa6a3c0447aeb9cc54cf6422ba32b294e5e1c3ef6d782f2acff4a70694c4d1663", 1], ["0x00588e8e1d18cba576a4d35758069fe94e53f638b6faf7c07b8abd2bc5c5cdee", 3]],
      // stake_pub - CBOR byte array
      2: "0xad4b948699193634a39dd56f779a2951a24779ad52aa7916f6912b8ec4702cee",
      // reward_address - CBOR byte array
      3: "0x00588e8e1d18cba576a4d35758069fe94e53f638b6faf7c07b8abd2bc5c5cdee47b60edc7772855324c85033c638364214cbfc6627889f81c4",
      // nonce
      4: 5479467
      // voting_purpose: 0 = Catalyst
      5: 0
    }
    

The entries under keys 1, 2, 3, 4 and 5 represent the Catalyst delegation array, the staking credential on the Cardano network, the address to receive rewards, a nonce, and a voting purpose, respectively. A registration with these metadata will be considered valid if the following conditions hold:

Delegation to the voting key 0xa6a3c0447aeb9cc54cf6422ba32b294e5e1c3ef6d782f2acff4a70694c4d1663 will have relative weight 1 and delegation to the voting key 0x00588e8e1d18cba576a4d35758069fe94e53f638b6faf7c07b8abd2bc5c5cdee relative weight 3 (for a total weight of 4). Such a registration will assign 1/4 and 3/4 of the value in ADA to those keys respectively, with any remainder assigned to the second key.

The registration witness depends on the type of stake credential used. To produce the witness field in case of a staking public key, the CBOR representation of a map containing a single entry with key 61284 and the registration metadata map in the format above is formed, designated here as sign_data. This data is signed with the staking key as follows: first, the blake2b-256 hash of sign_data is obtained. This hash is then signed using the Ed25519 signature algorithm. The witness metadata entry is added to the transaction under key 61285 as a CBOR map with a single entry that consists of the integer key 1 and signature as obtained above as the byte array value.

Witness example:

61285: {
      // witness - ED25119 signature CBOR byte array
      1: "0x8b508822ac89bacb1f9c3a3ef0dc62fd72a0bd3849e2381b17272b68a8f52ea8240dcc855f2264db29a8512bfcd522ab69b982cb011e5f43d0154e72f505f007"
    }
    

Metadata schema

See the schema file

Test vector

See test vector file

Future development

A future change of the Catalyst system may make use of a time-lock script to commit ADA on the mainnet for the duration of a voting period. The voter registration metadata in this method will not need an association with a staking credential. Therefore, the staking_credential map entry and the registration_witness payload with key 61285 will no longer be required.

Changelog

Fund 3 added the reward_address inside the key_registration field.

Fund 4:

It was planned that since Fund 4, registration_signature and the staking_pub_key entry inside the key_registration field will be deprecated. This has been deferred to a future revision of the protocol.

Fund 8:

This CIP is licensed under CC-BY-4.0