Support TLS connection to trusted peer

[cdhowie]

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Supporting a TLS connection to the trusted peer eliminates the need to trust either the network path or a VPN provider. It's likely much easier for users to run/find a full node with TLS support than it is to set up a VPN on an Android device.

[schildbach]

Afaik bitcoind still doesn't support TLS.

[cdhowie]

It is trivial to set up stunnel to provide this functionality against any full node implementation. (In fact I'd argue that bitcoind shouldn't implement TLS listening support. That's what stunnel is for.)

[schildbach]

@cdhowie Ok, you're right in that one could use stunnel, and I probably would do that myself too. Still I think there should be something easy to use built into bitcoind. Recently, I learned there is something on the way: https://gist.github.com/jonasschnelli/c530ea8421b8d0e80c51486325587c52 (also see discussion on the bitcoin-devel list).

In any case this would need to be built into bitcoinj, rather than an app like Bitcoin Wallet. For apps, this should be almost transparent (except maybe some TLS info in the network monitor). Please feel free to submit a PR.