Perun14

Alan W

function CheckSignature(address verifier, uint vid, address p1, uint cash1, uint subchan1, address Ingrid,
                                address p2, uint cash2, uint subchan2, uint validity, uint version, bytes sig) private view returns (bool) {
    bytes32 msgHash = keccak256(vid, p1, cash1, subchan1, Ingrid, p2, cash2, subchan2, validity, version);
    return libSignatures.verify(verifier, msgHash, sig);
}

function CheckVersion(address verifierA, address verifierB, uint vid, VirtualContract memory vc, uint version, bytes sigA, bytes sigB) private view returns (bool) {
    if (!CheckSignature(verifierA, vid, vc.p1, vc.cash1, vc.subchan1, vc.Ingrid, vc.p2, vc.cash2, vc.subchan2, vc.validity, version, sigA))
        return false;
    bytes32 msgHash = keccak256(vid, vc.p1, vc.cash1, vc.subchan1, vc.Ingrid, vc.p2, vc.cash2, vc.subchan2, vc.validity, version, sigA);
    return libSignatures.verify(verifierB, msgHash, sigB);
}

function CheckVC(uint vid, address p1, uint cash1, uint subchan1, address Ingrid,
                           address p2, uint cash2, uint subchan2, uint validity, bytes sig) private view {
    require(id == subchan1 || id == subchan2);
    require(Ingrid == alice.id || Ingrid == bob.id);
    require(Other(Ingrid, alice.id, bob.id) == p1 || Other(Ingrid, alice.id, bob.id) == p2);
    // require(alice.id == p1 && bob.id == p2 || alice.id == p2 && bob.id == p1)
    // it could be that Ingrid == alice.id, bob.id == p1 but p2 == a random address
    require(CheckSignature(Other(msg.sender, alice.id, bob.id), vid, p1, cash1, subchan1, Ingrid, p2, cash2, subchan2, validity, 0, sig));
}

function Other(address p, address p1, address p2) private pure returns (address) {
    if (p == p1) return p2;
    else return p1;
}