Opened 5 years ago

#229 new task

Need to decide the nature of the puzzle

Reported by: ynir.ietf@… Owned by: draft-ietf-ipsecme-ddos-protection@…
Priority: normal Milestone:
Component: ddos-protection Severity: Active WG Document
Keywords: Cc:

Description

Current text has PRF based puzzles: for a given cookie and difficulty leve l, find a key k, such that PRF(k, cookie) has at least l trailing zero bits. The problem with this puzzle is that while the expected time to solve this puzzle is 2l, the actual time varies wildly.

Scott Fluhrer suggested ([1]) that we use another kind of puzzle that is closer to constant-time. That requires more up-front work on the part of the responder (creating a new opportunity for DoS?) and larger IKE_SA_INIT requests. IKE_SA_INIT requests are not protected by IKEv2 fragmentation

[1] http://www.ietf.org/mail-archive/web/ipsec/current/msg09601.html

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