Skip to main content

Idena smart contracts#

Note: Currently only predefined smart contracts available (see below).

Gas and Transaction fee#

In addition to transaction fee per byte a gas consumption has to be paid when a smart contract is called.

Transaction fee and gas charged when calling the following for smart contracts:

maxFee parameter#

Maximum transaction fee maxFee parameter must cover a sum of txFee+gasCost.

GasCost is calculated as a total amount of gas consumed by the smart contract operations multiplied to the current GasPrice.

You can use estimation methods to get an expected amount of gas that will be consumed by the smart contract:

Response example:

"result": {
...
"gasCost": "0.416",
"txFee": "0.56"
}

The maxFee parameter can be omitted when calling estimation methods.

GasPrice#

GasPrice is calculated automatically by the protocol. The minimum GasPrice is: GasPrice= 0.01/NetworkSize.

The bcn_feePerGas method should be called to get the current GasPrice.

Example:

{
"result": 1651527663100 //0.0000016515276631 iDNA
}

Smart contract stake#

In order to deploy a new Idena smart contract stake must be locked. The amount parameter has to be specified to lock the stake when DeployTx transaction is called. If the specified amount is less than a minimum stake then error message will be returned.

"error": {
"code": -32000,
"message": "invalid amount"
}

Minimum smart contract stake is calculated as GasPrice * 3000000

50% of the stake will be refunded to its creator once the smart contract is terminated.

Smart contract termination#

Termination of the smart contract removes all smart contract data from the state. 50% of the stake is burnt. Another 50% of the stake transferred to the creator of the smart contract.

The contract might be terminated according to its internal rules.

For instance OracleVoting smart contract can be terminated after a termination delay once the public voting is finished. Termination delay is proportional to the amount of coins blocked at the smart contract stake. Termination delay, days = round( (NetworkSize * Stake) ^ 1/3 )

Predefined smart contracts#

Currently only predefined smart contracts available to deploy. You can find the code of the smart contracts here.

CodeHash represents the algorithm of a predefined smart contract:

Smart contracts transactions#

  • DeployTx: Create smart contract
  • CallTx: Call method of the smart contract
  • TerminateTx: Delete smart contract and refund 50% of the locked stake

Smart contracts transaction receipt#

TxReceipt indicates result of mined smart contract transaction DeployTx, CallTx or TerminateTx

{
"contract": "0xa9694569a6efe69f156a9f457bbd2163c78e4ef4",
"method": "transfer",
"success": true,
"gasUsed": 382,
"txHash": "0x7d48995a8f6a22e4d060a9471adc22e88e5303bb1129bf6c7a250438f370c5b5",
"error": "",
"gasCost": "114.6",
"txFee": "17.7"
}
  • Contract: address of the smart contract
  • Method: called method of the smart contract
  • Success: whether transaction changed the state or not
  • gasUsed: amount of gas used
  • txHash: smart contract transaction hash
  • Error: error text
  • gasCost: gas cost, iDNA
  • txFee: transaction fee, iDNA

Smart contract address#

You can calculate the address of the smart contract before it will be deployed as following:

const addr = toBuffer(hexToUint8Array(state.address));
const epoch = int16ToBuffer(parseInt(state.epoch));
const nonce = int32ToBuffer(parseInt(state.nonce));
const res = [...addr, ...epoch, ...nonce];
const hash = sha3.keccak_256.array(res);
response.address = toHexString(hash.slice(hash.length - 20), true);
  • addr: sender address
  • epoch: epoch when the smart contract will be deployed
  • nonce: nonce of the deploy transaction

Example:

{
"address": "0x6f73b00d873fc21c4ca2f44bfb20653768dbd48e",
"epoch": "1",
"nonce": "2"
}
{
"address": "0x39bd250ac33f24b32af705617c0b46ead3c8f7c5"
}
Edit this page