Use of Bit 0x20 in DNS Labels to Improve Transaction Identity

Document Type Expired Internet-Draft (individual)
Authors Paul Vixie  , David Dagon 
Last updated 2008-03-18
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Expired & archived
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The small (16-bit) size of the DNS transaction ID has made it a frequent target for forgery, with the unhappy result of many cache pollution vulnerabilities demonstrated throughout Internet history. Even with perfectly and unpredictably random transaction ID's, random and birthday attacks are still theoretically feasible. This document describes a method by which an initiator can improve transaction identity using the 0x20 bit in DNS labels.


Paul Vixie (
David Dagon (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)