Operation Ded Cat is on a mission of a quantum nature to raise awareness & understanding of OP_CAT. @OperationDedCat
OP_CAT was previously included in Bitcoin Script, but was disabled due to concerns over the potential of scripts
that grew too large. However, because of the addition of Tapscript's limitation on stack element size (520 bytes),
it is now once again feasible to reintroduce OP_CAT. Functionality wise, OP_CAT operation enables the
concatenation of two stack values. It fails if the stack has less than two values or the concatenated result
exceeds the 520-byte limit.
case OP_CAT:
{
if (stack.size() < 2)
return set_error(serror, 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;
We can use OP_CAT to create tree signatures. By combining multiple signatures and concatenating them, we can have more flexible multisigs. We are essentially creating a binary tree of signature, where each node is the concatenation of its two children nodes. This process continues up the tree. The total concatenated signature will be at the top of the tree (root) which we can then verify against the public key that represents the entire tree. This increases efficiency and reduces size because it reduces the number of signatures required in a transaction. This is a good way to use multisig wallets, where multiple users must authorize a transaction.
One potential concern as we advance technologically, specifically in regards to quantum computing, is how it can affect and break modern cryptography. However, securing data with a Lamport signature is believed to be quantum-resistant. Lamport signatures are one-time signatures that use a pair of large random numbers for each bit of the key. They are resistant to quantum computer attacks. The implementation details include generating a random set of numbers for each bit of the key. The message is then hashed, and using the hashed message, we select the according digits from the sets from our private key. Using OP_CAT, we can concatenate these selected numbers to form the Lamport signature. The public key is also derived from the private key, and verifiers can use the message’s hash to compare them with the signature. There are some caveats with using Lamport signatures, however. These signatures are significantly larger than traditional signatures, which may reduce blockchain efficiency/size.