This proof of concept tool has been released with the related blog post:

Is KAX17 performing de-anonymization Attacks against Tor Users?

It is a partial and quick and dirty proof of concept implementation of the following specifications to configure a tor client to use trusted exit relays only.

• https://nusenu.github.io/ContactInfo-Information-Sharing-Specification/#proof
• https://gitlab.torproject.org/tpo/core/torspec/-/blob/main/proposals/326-tor-relay-well-known-uri-rfc8615.md
• https://nusenu.github.io/tor-relay-operator-ids-trust-information (WIP DRAFT)

NOTE: This proof of concept is NOT fit for general use and not meant to be used by end-users!

This limited version only selects exit relays and leaves other positions unchanged. It supports a max_depth of 0 only (no recusion to find trusted operators).

this proof of concept code performs the following steps

• reads the trust configuration and validation cache
• connects to a local tor client via it's ControlPort to find relays claiming to be from a trusted operator
• validates claims via HTTPS (routed via tor) or DNS including DNSSEC check (can also be routed via tor but requires dnscrypt-proxy)
• writes a validation cache to disk
• configures the local tor client (non-persistently) to only use exits from trusted operators that passed the validation steps

requirements

• a local tor client must be running (see sample torrc file)
• dnssec-root-trust must contain the DNSSEC Root Trust Anchor (IANA)
• local dnscrypt-proxy daemon, configured to route (encrypted) DNS via tor's SOCKSPort

force_tcp = true

proxy = 'socks5://127.0.0.1:9050'

...

configuration

• this PoC comes with an empty trust_config file, users need to add entries (example)
• dnscrypt-proxy is expected to listen on 127.0.2.1:53 otherwise configure the IP address in the resolv.conf file
• generate a password hash via tor --hash-password randomstringgoeshere and paste it into the torrc config (or use ControlSocket instead)
• add the plaintext password to the controller_password= line in the script
• torcontactinfoparser needs to be installed manually
• on debian pyunbound is in the python3-unbound package

used libraries

• stem
• torcontactinfoparser
• pyunbound for DNSSEC validation
• requests (with pysocks support)
• urllib