Precompile Contracts

On top of a set of opcodes, EVM also offers advanced functionalities through precompiled contracts. These are special contracts bundled with EVM at fixed addresses that can be called with a determined gas. The gas is purely the contractual cost, neither the cost of the call itself nor the instructions to put the parameters in memory.

Precompiled contract addresses start from 1 and increment for each contract. New hardforks may introduce new precompiled contracts. Similar to the regular contracts, new contracts are called from opcodes with instructions, such as CALL.

For all precompiled contracts, inputs that are shorter than expected are assumed to be virtually padded with zeros at the end, whereas any surplus bytes at the end of inputs that are longer than expected are ignored.

The address precompile contract is described by the last 2 bytes:

Byte range [0..18]	Byte range [18..20]
000000000000000000000000000000000000	addr

EcRecover

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000001	3000	hash, v, r, s	publicAddress

EcRecover is a elliptic curve digital signature algorithm (ECDSA) public key recovery function. For details, see this page.

SHA2-256

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000002	60	data	hash

SHA2-256 is the hash function used in Bitcoin. For details, see this page

RIPEMD-160

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000003	600	data	hash

A hash function. For details, see this page.

Identity

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000004	15	data	data

Identity copies and returns input data. For details, see this page.

Modexp

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000005	200	Bsize, Esize, Msize, B, E, M	value

Modexp is an arbitrary-precision exponentiation under modulo. For details, see this page.

EcAdd

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000006	150	x1, x2, y1, y2	x, y

EcAdd is the point addition (ADD) on the elliptic curve alt_bn128. For details, see this page.

EcMul

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000007	6000	x1, x2, s	x, y

EcMul is the scalar multiplication (MUL) on the elliptic curve alt_bn128. For details, see this page.

EcPairing

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000008	45000	x1, y1, x2, y2, …, xk, yk	success

EcPairing is the bilinear function on groups on the elliptic curve alt_bn128. For details, see this page.

Blake2f

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000009	0	rounds, h, m, t, f	h

Blake2f is the compression function F used in the BLAKE2 cryptographic hashing algorithm. For details, see this page.

GetHeader

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000102	42000	hash	header view

Get the header of a relayed CKB block header by hash.

Inputs

Click here to view ABI

struct Input {
    bytes32 hash;
}

Output

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struct Header {
    uint32 version;
    uint32 compactTarget;
    uint64 timestamp;
    uint64 number;
    uint64 epoch;
    bytes32 parentHash;
    bytes32 transactionsRoot;
    bytes32 proposalsHash;
    bytes32 extraHash;
    bytes32 dao;
    uint128 nonce;
    bytes extension;
    bytes32 blockHash;
}

Example

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contract GetCkbHeader {
    event GetHeaderEvent(CKBHeader);
    event NotGetHeaderEvent();

    int8 ret;

    function getHeader(bytes32 blockHash) public returns (CKBHeader memory) {
        address get_header_addr = address(0x0102);
        (bool isSuccess, bytes memory res) = get_header_addr.staticcall(
            abi.encode(blockHash)
        );

        CKBHeader memory header;
        if (isSuccess) {
            header = abi.decode(res, (CKBHeader));
            emit GetHeaderEvent(header);
        } else {
            emit NotGetHeaderEvent();
        }
        return header;
    }
}

GetCell

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000103	42000	out point	cell info

Get the relayed cell information by out point.

Inputs

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struct OutPoint {
    bytes32 txHash;
    uint32 index;
}

Output

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struct CellInfo {
    OutPoint outPoint;
    CellOutput output;
    bytes data;
}

struct CellOutput {
    uint64 capacity;
    Script lock;
    Script[] type_;
}

Example

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contract GetCkbCell {
    event GetCellEvent(OutPoint);
    event NotGetCellEvent();

    int8 ret;

    function getCell(bytes32 blockHash) public returns (CellInfo memory) {
        address get_cell_addr = address(0x0103);
        (bool isSuccess, bytes memory res) = get_cell_addr.staticcall(
            abi.encode(outPoint)
        );

        CellInfo memory cell;
        if (isSuccess) {
            cell = abi.decode(res, (CellInfo));
            emit GetCellEvent(cell);
        } else {
            emit NotGetCellEvent();
        }
        return cell;
    }
}

CallCkbVm

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000104	300	cell dep, args	big-endian bytes

Call a script that runs in CKB-VM and return the execute result.

Inputs

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struct CellDep {
    OutPoint outPoint;
    uint32   index;
}

struct InputArgs {
    bytes[] args;
}

Output

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struct Result {
    int8 ret;
}

Example

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contract CallCkbVm {
    event CallCkbVmEvent(int8);
    event NotGetCellEvent();

    int8 ret;

    function testCallCkbVm(
        bytes32 txHash,
        uint32 index,
        uint8 depType,
        bytes[] memory input_args
    ) public {
        OutPoint memory outPoint = OutPoint(txHash, index);
        (bool isSuccess, bytes memory res) = address(0x0104).staticcall(
            abi.encode(CellDep(outPoint, depType), input_args)
        );

        if (isSuccess) {
            ret = int8(uint8(res[0]));
            emit CallCkbVmEvent(ret);
        } else {
            emit NotGetCellEvent();
        }
    }

    function callCkbVm() public view returns (int8) {
        return ret;
    }
}

CkbBlake2b

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000106	60	data	hash

Calculate the ckb-blake2b hash.

Inputs

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struct Input {
    byte[] data;
}

Output

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struct Output {
    bytes32 hash;
}

CkbMbtVerify

ADDRESS	MINIMUM GAS	INPUT	OUTPUT
0x0000000000000000000000000000000000000107	56000	verify proof payload	bool

Verify the CKB merkle binary tree proof.

Inputs

Click here to view ABI

struct VerifyProofPayload {
    uint8 verifyType;
    bytes32 transactionsRoot;
    bytes32 witnessesRoot;
    bytes32 rawTransactionsRoot;
    Proof proof;
}

struct Proof {
    uint32[] indices;
    bytes32[] lemmas;
    bytes32[] leaves;
}

If the verify_type is 0, the leaves should be in the rawTransactionsRoot, otherwise in the witnessesRoot.

Output

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struct Output {
    bool ret;
}

Example

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contract VerifyCMBTRoot {
    event VerifyCMBTRootEvent(bool);
    event NotVerifyCMBTRootEvent();

    int8 ret;

    function verifyCMBTRoot(VerifyProofPayload payload) public returns (bool) {
        address get_cell_addr = address(0x0107);
        (bool isSuccess, bytes memory res) = get_cell_addr.staticcall(
            abi.encode(payload)
        );

        if (isSuccess) {
            emit VerifyCMBTRootEvent(isSuccess);
        } else {
            emit NotVerifyCMBTRootEvent();
        }
        return isSuccess;
    }
}