[Whonix-devel] RFC 6528 revision for better system privacy

[bancfc at openmailbox.org]

Hi Steven and Fernando,

I am a Whonix (anonymity OS) dev and would like to discuss the RFC 6528 
[0] you worked on. There has been privacy research in the area of timer 
and clock leaks in network protocols that can aid adversaries in 
deanonymizing Tor clients and hidden services. There is a practical 
attack where an adversary can skew timer measurements by overloading 
target machines and affect the oscillation of timer crystals in 
predictable patterns that can be remotely measured in TCP sequence 
numbers.[1]

Please consider revising the RFC to omit the requirement of xoring timer 
output with TCP ISNs. Recently the Linux kernel gained the SipHash PRF 
to generate better sequence numbers and deprecated MD5. This further 
reduces the necessity of including timer input which has become a side 
channel that aids traffic correlation and endangers privacy focused use 
cases.


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[0] https://tools.ietf.org/html/rfc6528
[1] http://sec.cs.ucl.ac.uk/users/smurdoch/papers/ccs06hotornot.pdf
[2] http://sec.cs.ucl.ac.uk/users/smurdoch/papers/ih05coverttcp.pdf