According to the developers, such attacks exploit the asymmetric nature of the rendezvous protocol, which makes it difficult to protect against them. This problem cannot be solved with simple code modifications, which will require fundamental changes to the Tor codebase.
Another proposed measure is the implementation of a Proof-Of-Work (POW) system, which will prevent an attacker from causing an onion service to malfunction, but at the same time normal clients will be able to access them only with a slight delay.
According to Tor Project developer George Kadianakis, although both options have their drawbacks, they are compatible and can be implemented together.
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