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Diffstat (limited to 'spec/padding-spec/overview.md')
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diff --git a/spec/padding-spec/overview.md b/spec/padding-spec/overview.md new file mode 100644 index 0000000..594b9d4 --- /dev/null +++ b/spec/padding-spec/overview.md @@ -0,0 +1,28 @@ +<a id="padding-spec.txt-1"></a> + +# Overview + +Tor supports two classes of cover traffic: connection-level padding, and +circuit-level padding. + +Connection-level padding uses the PADDING cell command for cover +traffic, where as circuit-level padding uses the DROP relay +command. PADDING cells are single-hop only and can be differentiated from +normal traffic by Tor relays ("internal" observers), but not by entities +monitoring Tor OR connections ("external" observers). + +DROP relay messages are multi-hop, and is not visible to intermediate Tor +relays, because the relay command field is covered by circuit layer +encryption. Moreover, Tor's 'recognized' field allows DROP messages +to be sent to any intermediate node in a circuit (as per Section +6.1 of tor-spec.txt). + +Tor uses both connection level and circuit level padding. Connection +level padding is described in section 2. Circuit level padding is +described in section 3. + +The circuit-level padding system is completely orthogonal to the +connection-level padding. The connection-level padding system regards +circuit-level padding as normal data traffic, and hence the connection-level +padding system will not add any additional overhead while the circuit-level +padding system is actively padding. |