Given that they've already decided to include support in Chrome itself for accessing USB hardware security tokens for U2F, I see no reason why they couldn't do the same with End to End + OpenPGPCards like the Yubikey NEO, which happens to also be a U2F device.<p>It would provide a solution to some of the issues they document on their own Wiki regarding secret keys being stolen by an attacker through another Chrome extension, another application on the system, etc.<p>EDIT: YES! I missed this part[1] in the Wiki earlier:<p>"Additionally, we plan to add remote private key support in the future. When support for that is ready, high-risk users could protect their secret keys (stored, e.g., in a hardware USB device) from compromise even when an adversary introduces a backdoor in the source code."<p>[1] <a href="https://github.com/google/end-to-end/wiki/Threat-model#backdoor-in-end-to-end-source-code" rel="nofollow">https://github.com/google/end-to-end/wiki/Threat-model#backd...</a>