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Simple plasma implementation

Plasma consists of three major parts. 1. Plasma chain: A simple proof-of-authority chain where the actual transactions take place. 2. Plasma contract: A smart contract deployed on root chain which handles the deposits and withdrawals for the child chain (plasma chain). 3. Ethereum blockchain: The root chain which only records the block headers of the plasma chain.

The complete cycle of interacting with plasma is made up of three stages.


Participants deposit to the plasma contract on the root chain. Then the operator at the plasma chain will construct a deposit transaction according to the contract event when building a new block.


Participants could transact with each other on the plasma chain without notifying the root chain. Only when every block is created by the operator, it will submit the block header to the plasma contract on the root chain.


A withdrawal is initiated by calling the plasma contract. After creating a withdrawal, user needs to wait 7 days for other participants to challenge it. If anyone could prove the given withdrawal that has been spent later on the plasma chain, the withdrawal will be canceled. Otherwise, after 7 days and without any other withdrawals with higher priority, user could withdraw his funds back to the root chain.


  1. Truffle: An Ethereum development framework which helps us compiling, deploying, and interacting with smart contract.
  2. Testrpc: A test Ethereum RPC client for fast development. Here, we use ganache-cli. If you prefer a GUI version, you could replace it with ganache. Note that you could also launch an Ethereum private chain (geth) to replace testrpc.


  1. Install dependency
    npm install
  2. Run ganache
    Testrpc will generate ten default accounts for us. For convenience, you could specify a HD wallet mnemonic to get fixed addresses. For example:
    ganache-cli -m pink two example move shop length clean crop cheese tent strike field
    The corresponding initial addresses are:
    (0) 0x0bf5f0f213b0b752858e9352fd6081f5d730dc17
    (1) 0x87dbd8ab1bd9d4fce07db12743594a5f456435ff
    (2) 0x3b0ba3134ac12cc065d4dba498a60cba5ef16098
    (3) 0x6c7f749d0e21aa6478af8e7adc362a8bf76be826
    (4) 0x9a404f89ad853e592d7b48242b4745c17a8ee852
    (5) 0x34d5e94fc3e7ecac3859a03176cb57534f30b71c
    (6) 0x8c0e1d37680a03eeb4c85880ffe1edf61ffa76f4
    (7) 0x6017db4acdfed284da94485d715a0f758048ac0b
    (8) 0x239ddceb1d7cebf07435a52f569b86f310af9cad
    (9) 0x1166d1f78f44c79e8e3f0d74419940e521790d7c
  3. Compile contracts
    truffle compile
  4. Deploy contracts

    truffle migrate
    If you need to deploy contracts on this testrpc again, don't forget to add the
  5. Set the contract configuration (config.js).

    1. After deploying contracts, fill in the
      contract address.
    2. Choose one of the initial addresses as the operator address, for example,
  6. Run the plasma chain.

    npm start
    node main.js [options]
    the available options are:

|Option|Description| |---|---| |--port|Specify HTTP API port, default 3001| |--contract|Specify contract address, otherwise use value in config.js| |--operator|Specify operator address, otherwise use value in config.js|


  1. Run ganache

  2. Run tests

    truffle test


Block related

Get blockchain

Get the whole blockchain.



curl http://localhost:3001/blocks

Mine blocks

Miner mines a new block.



curl -X POST http://localhost:3001/mineBlock

Transaction related

Create a transaction

Create a transaction to other participants. User could specify at most two UTXOs to spend. Also note that the units used in field

is ether.

|Name|Type|Required|Description| |---|---|---|---| |from|Address|Yes|Transfer funds from whom| |to|Address|Yes|Transfer funds to whom| |amount|Decimal|Yes|How much ether (in ether)|

curl -H "Content-type:application/json" --data '{"from": "0x6C7f749d0E21aA6478aF8e7Adc362a8bF76Be826", "to": "0x3B0bA3134Ac12Cc065d4dBa498a60cba5Ef16098", "amount": 2}' http://localhost:3001/transact

Deposit related


Deposit funds to Plasma smart contract.


|Name|Type|Required|Description| |---|---|---|---| |address|Address|Yes|Deposit from whom| |amount|Integer|Yes|How much funds to deposit|

curl -H "Content-type:application/json" --data '{"address": "0x6C7f749d0E21aA6478aF8e7Adc362a8bF76Be826", "amount": 4}' http://localhost:3001/deposit

Withdrawal related

Create withdrawal

Create a new withdrawal.


|Name|Type|Required|Description| |---|---|---|---| |blkNum|Integer|Yes|The position of the UTXO user wants to withdraw| |txIndex|Integer|Yes|The position of the UTXO user wants to withdraw| |oIndex|Integer|Yes|The position of the UTXO user wants to withdraw| |from|Address|Yes|The owner of the UTXO|

curl -H "Content-type:application/json" --data '{"blkNum": 3, "txIndex": 1, "oIndex": 0, "from": "0x6C7f749d0E21aA6478aF8e7Adc362a8bF76Be826"}' http://localhost:3001/withdraw/create

Challenge withdrawal

Create a withdrawal challenge.


|Name|Type|Required|Description| |---|---|---|---| |withdrawalId|Integer|Yes|The withdrawal ID user wants to challenge| |blkNum|Integer|Yes|The position of the UTXO user wants to challenge| |txIndex|Integer|Yes|The position of the UTXO user wants to challenge| |oIndex|Integer|Yes|The position of the UTXO user wants to challenge| |from|Address|Yes|The owner of the UTXO|

curl -H "Content-type:application/json" --data '{"withdrawalId": 4000000000, "blkNum": 4, "txIndex": 2, "oIndex": 1, "from": "0x6C7f749d0E21aA6478aF8e7Adc362a8bF76Be826"}' http://localhost:3001/withdraw/challenge

Finalize withdrawal

Finalize withdrawals manually.


|Name|Type|Required|Description| |---|---|---|---| |from|Address|Yes|Who initiates the withdrawal finalization|

curl -H "Content-type:application/json" --data '{"from": "0x6C7f749d0E21aA6478aF8e7Adc362a8bF76Be826"}' http://localhost:3001/withdraw/finalize

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