in src/XDM.ts [213:223]
constructor(postToWindow: Window, targetOrigin?: string) {
this.postToWindow = postToWindow;
this.targetOrigin = targetOrigin;
this.registry = new XDMObjectRegistry();
this.channelId = nextChannelId++;
if (!this.targetOrigin) {
this.handshakeToken = newFingerprint();
}
}