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ccip-005-citycoins-sip-010-token.md

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CCIP-005

Preamble

CCIP Number 005
Title CityCoins SIP-010 Token
Author(s) Jason Schrader [email protected]
Consideration Technical, Economic
Type Standard
Status Ratified
Created 2022-03-16
License BSD-2-Clause

Introduction

The Stacks blockchain is a Layer 1 blockchain connected to Bitcoin, in which miners spend Bitcoin to bid for and win a fixed amount of Stacks tokens. Stackers have the option to lock up Stacks tokens for a specified amount of time, and in turn, receive a portion of the Bitcoin spent by miners proportionate to the amount Stacked1.

Taking this concept a level further, a new token (a "CityCoin") is created on the Stacks blockchain, following the SIP-010 fungible token standard2, such that CityCoins can be mined and Stacked per the methods stated above except a portion of the miner's bid would be redirected to the city's wallet overseen by a trusted third party custodian.

CityCoins leverage similar properties from the Proof of Transfer (PoX) consensus mechanism3 of the Stacks blockchain, programmed through a smart contract in Clarity.

This proposal describes the token functionality for a CityCoin.

Specification

Token Configuration

CityCoins are fungible tokens on the Stacks blockchain that adhere to the SIP-010 fungible token standard2. This includes specific functions defined in the SIP for transfer, name, symbol, decimals, balances, total supply, and token URI.

CityCoins do not have any decimal places and 1 CityCoin represents the smallest unit.

The token URI can only be updated from the auth contract.

CityCoins can be sent and received on the Stacks blockchain, interact with smart contracts, and be used by any interface that accepts a SIP-010 fungible token.

CityCoins also follow the CityCoin Token Trait, defined in CCIP-001.

Within the token contract are variables to track:

  • the number of Stacks blocks before a halving occurs
  • the Stacks block thresholds set for each halving
  • the activation status of the token contract
  • the core contract states

Token Activation

Once a CityCoin is deployed and activated, the emission schedule begins starting from the activation block height of the CityCoin core contract.

More information about Activation can be found in CCIP-002.

CityCoins have no ICO, no pre-sale, and no pre-mine. CityCoins are only mined into existence.

Emissions Schedule

Miners receive coinbase rewards for mining the CityCoin outlined in the table below. The "halvings" occur at intervals similar to Bitcoin and Stacks, every 210,000 blocks, and there is a 10,000 block bonus reward for early miners.

The issuance schedule does not begin until mining is activated, and once it begins, the current block height of the Stacks blockchain is recorded in the contract. From there, the issuance continues as follows:

Time Period Reward Notes
First 10,000 Stacks Blocks 250,000 CityCoins approx. 3 months
Next 200,000 Stacks Blocks 100,000 CityCoins approx. 4 years, minus bonus period
Next 210,000 Stacks Blocks 50,000 CityCoins approx. 4 years
Next 210,000 Stacks Blocks 25,000 CityCoins approx. 4 years
Next 210,000 Stacks Blocks 12,500 CityCoins approx. 4 years
Next 210,000 Stacks Blocks 6,250 CityCoins approx. 4 years
After 1,050,000 Stacks Blocks 3,125 CityCoins continues indefinitely

After the final halving at 1,050,000 Stacks blocks past the Stacks block height recorded at activation, the total supply is estimated to be 42,187,500,000 and will increase indefinitely by 164,062,500 per year.

Backwards Compatibility

None, this is the initial implementation.

Activation

None, this is the initial implementation.

Reference Implementations

  • miamicoin-token deployed on the Stacks mainnet4, implementing:

    • the SIP-010 functions on lines 018-059
    • the citycoin-token-trait on lines 081-146, 153-179

  • newyorkcitycoin-token deployed on the Stacks mainnet5, implementing:

    • the SIP-010 functions on lines 019-060
    • the citycoin-token-trait on lines 082-144, 151-177

Footnotes

Footnotes

  1. https://stacking.club ↩

  2. https://github.com/stacksgov/sips/blob/main/sips/sip-010/sip-010-fungible-token-standard.md ↩ ↩2

  3. https://docs.stacks.co/understand-stacks/proof-of-transfer ↩

  4. https://explorer.stacks.co/txid/SP466FNC0P7JWTNM2R9T199QRZN1MYEDTAR0KP27.miamicoin-token?chain=mainnet ↩

  5. https://explorer.stacks.co/txid/SP2H8PY27SEZ03MWRKS5XABZYQN17ETGQS3527SA5.newyorkcitycoin-token?chain=mainnet ↩