Let's Downgrade Let's Encrypt
Tianxiang Dai, Haya Shulman, Michael Waidner · 2021
Following the recent off-path attacks against PKI, Let's Encrypt deployed in 2020 domain validation from multiple vantage points to ensure security even against the stronger on-path MitM adversaries. The idea behind such distributed domain validation is that even if the adversary can hijack traffic of some vantage points, it will not be able to intercept traffic of all the vantage points to all the nameservers in a domain.