Tor Revamps Guard Selection Algorithm to Resist Guard-Capture Attacks

The Tor 0.3.0 stable series also deprecates the use of old RSA1024 keys for both relays and clients, which now make use of Ed25519 keys to authenticate their link connections to relays. As such, the default for AuthDirPinKeys is now 1, and it looks like circuit crypto has been Curve25519-authenticated. Moreover, Tor 0.3.0 lays more groundwork for the upcoming next-generation hidden services by enabling handling of ESTABLISH_INTRO v3 cells, along with support for the HSDir version 3 protocol for all Tor relays, allowing storing and serving of version 3 descriptors.