TCP Stealth

Document Type Expired Internet-Draft (individual)
Last updated 2015-07-21 (latest revision 2015-01-17)
Stream (None)
Intended RFC status (None)
Expired & archived
plain text pdf html
Stream Stream state (No stream defined)
Document shepherd No shepherd assigned
IESG IESG state Expired
Telechat date
Responsible AD (None)
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


TCP servers are visible on the Internet to unauthorized clients, as the existence of a TCP server is leaked in the TCP handshake before applications have a chance to authenticate the client. We present a small modification to the initial TCP handshake that allows TCP clients to replace the TCP ISN in the TCP SYN packet with an authorization token. Based on this information, TCP servers may then chose to obscure their presence from unauthorized TCP clients. This RFC documents the specific method for calculating the authorization token to ensure interoperability and to minimize interference by middleboxes. Mandating support for this method in operating system TCP/IP implementations will ensure that clients can connect to TCP servers protected by this method.


Julian Kirsch (
Christian Grothoff (
Jacob Appelbaum (
Holger Kenn (

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