Bitroot VM

The Bitroot VM is a virtual machine running on the Bitcoin blockchain that provides programmable capabilities for Bitcoin Native Assets, including asset minting, issuance, transfer, and management.

Asset Management: Users can issue and manage their own Bitcoin Native Assets through the Bitroot protocol, similar to standards such as ERC-20 or ERC-721 on Ether

Lower Barrier: Bitroot lowers the barrier to issuing and managing digital assets by providing a more user-friendly interface and interactive experience, eliminating the need for users to learn smart contracts or the Bitcoin scripting language.

Consensus Security: Bitroot assets are protected by Bitcoin consensus.

The Bitroot VM represents a significant step forward in bringing smart contracts to Bitcoin, and at its core relies on the OP_CAT opcode. To make it easier to understand, Bitroot VM provides a one-stop Bitcoin service centre. Through a convenient, easy-to-interact UI design, Bitroot VM has a built-in DEX based on the Bitcoin network, which allows users to issue, manage, and trade Bitcoin protocol assets directly from a single website. As Bitroot VM expands, it will support other mainstream Bitcoin native assets and more lightweight Dapp applications.

OP_CAT

OP_CAT is a Bitcoin opcode that Satoshi Nakamoto included in the original Bitcoin stack, but removed in 2010.2023 In October 2023, a proposal surfaced to reintroduce OP_CAT by redefining the existing current opcode OP_SUCCESS126 as OP_CAT as the opcode for Tapscript, the scripting language used to support transactions in Taproot.

case OP_CAT:
{
    if (stack.size() <2 )
        return set_error(serrot, SCRIPT_ERR_INVALID_STACK_OPERATION);
    valtype& vch1 = stacktop(-2);
    valtype& vch2 = stacktop(-1);
    if (vch1.size() + vch2.size() > MAX_SCRIPT_ELEMENT_SIZE)
        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
    vch1.insert(vch1.end(), vch2.begin(), vch2.end());
    stack.pop_back();
}
break;

Satoshi Nakamoto initially removed OP_CAT because it was theoretically possible for a user to push an exponential amount of data onto the Bitcoin blockchain using that opcode, leading to a denial-of-service (DoS) attack. Now, however, tapscript allows up to 520 bytes of data to be contained in a single stack (a stack is simply a data structure for Bitcoin transactions), so Bitcoin 2021's Taproot upgrade invalidates the original DoS vector.

OP_CAT operates by allowing Bitcoin users to concatenate (in computer science terms, concatenate) two data points together and place those values at the top of the stack, which makes those values the first items that come into play during a transaction. Tandem values on the stack ensure that the associated bitcoin can only be used if certain conditions are met.

The reintroduction of OP_CAT provides Bitcoin with a powerful tool to support projects like BitVM, whose recently introduced concept of verifying arbitrary computations on Bitcoin will be made simpler and more efficient by OP_CAT. The Bitcoin ecosystem enables the creation of more versatile and expressive smart contracts.

With OP_CAT, it is possible to implement so-called smart contracts, which set predefined conditions for a specific bitcoin output. This not only opens the door to new scaling approaches, such as Blockstream's Ark, but also supports many other innovative approaches that rely on smart contracts. In addition, this marks Bitcoin as more than just a payment network, but also as a versatile and scalable computing platform.

OP_CAT (BIP-420) is currently live on Bitcoin's official test network, SIGNET, on 1 May 2024, allowing developers to build advanced OP_CAT applications using CatVM and test them in real-time on the official test network.