Commission contract on BSV

We are Alice Introduced a novel way , allow Bob Use her UTXO/ COINS , Without the need to Bob Provide her private key .Alice sign Bob The public key , So as to delegate the power of expenditure to Bob. Delegates have many use cases . for example , The user can authorize the app to spend on her behalf BSV. perhaps , The CFO wants the department head to release the funds allocated to the Department .

entrust

before , We developed a method , Give Way Alice Use her bitcoin private key in the transaction Sign any message . For delegated work , The message is just Bob The public key . By signing Bob The key of ,Alice Delegate the right to use her coins to Bob¹.

When Alice When you want to delegate , She first locked the funds into the following contracts .

import "./oracle.scrypt";

contract Delegate {
    
    PubKey owner;

    public function delegate(Sig ownerSig, PubKey delegate, Sig delegateSig, PubKey derivedPubKey, PubKey X, int lambda, SigHashPreimage txPreimage) {
    
        
        // ensure delegate's public key is signed by the owner
        require(Oracle.verifyData(delegate, ownerSig, this.owner, derivedPubKey, X, lambda, txPreimage));

        // delegate signs
        require(checkSig(delegateSig, delegate));
    }
}

Entrustment contract

She signed with her private key Bob The public key , That is to say 6 Yes ownerSig. She gave the partially signed transaction to Bob.Bob Put his signature （ The first 6 Yes delegateSig） Add to the transaction and broadcast it to spend locked in funds . The first 10 Line validation Bob The public key of is signed ², And therefore get Alice Authorization of . The first 13 Line check Bob The signature of the .

Please note that , Delegation does not create any on chain transactions , This only happens in Bob The actual cost UTXO when .

If Alice Want to spend on your own UTXO, She can simply delegate to herself by signing her own public key . therefore , She can be in Bob Revoke the delegation before moving the coin .

Delegation and multi signature

And Alice and Bob Between the traditional 2-of-2 Multi signature compared to , The above contract can be entrusted to anyone （ for example , Entrusted to Charlie or Dave）, Even in creating UTXO And then again . The trustee is undetermined , You can choose at will , Multi signature must know all the trustees in advance , You can't change it later . Delegation is more flexible .

Multiple commissions

stay Alice Entrusted to Bob after ,Bob Entrusted to Charlie,Charlie Re entrust to Dave, And so on .

The following modified contract allows multiple entrustments ：

contract Delegate {
    
    PubKey owner;

    static const int N = 3;

    public function delegateN(Sig[N] ownerSig, PubKey[N] delegate, Sig delegateSig, PubKey[N] derivedPubKey, PubKey[N] X, int[N] lambda, SigHashPreimage txPreimage) {
    
        
        PubKey lastDelegate = this.owner;
        loop (N) : i {
    
            PubKey owner = i == 0 ? this.owner : delegate[i - 1];
            // check if the next delegate is delegated by the current delegate
            if (Oracle.verifyData(delegate[i], ownerSig[i], owner, derivedPubKey[i], X[i], lambda[i], txPreimage))
                lastDelegate = delegate[i];
        }
        
        // last delegate signs
        require(checkSig(delegateSig, lastDelegate));
    }
}

Basically ,Alice signed Bob The public key ,Bob signed Charlie The public key ,…… The first 13 Line validation signature , To validate the delegate as before . Only the last representative is in 18 You can only spend coins by signing .

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[1] Alternative signature algorithms can also be used , for example Rabin Signature .

[2] Be careful Oracle.verifyData() Use... Internally SIGHASH_NONE, therefore Bob You can add whatever output he wants .