Querying the DNS from multiple vantage points to address local attackers

[roland]

Hey! There has also been some previous discussion of this in the thread linked below. Part of the original design of Boulder (the Let's Encrypt backend service) was to use multiple Validation Authorities (the servers that preform challenge validation) that must agree about the status of a challenges outcome. The design work for this is still ongoing as it presents a somewhat complex engineering problem within the current implementation.

Continuing the discussion from How do you confirm the person asking for the certificate actually owns the domain?:

@schoen

@NOYB,

An attacker would still only need to know one path or location, the destination, wouldn't they?

Nope, the attacker would need to make the attacker's server look like the real server from the perspective of each validation server that we used, which could be n different and independent paths. They don't simply have to knock the genuine server offline; instead, they have to be able to be seen as the genuine server by each validation server.