Module padding 

Definitions for circuit padding.

This module defines the API for a circuit padder, which is divided into two parts: a PaddingController and PaddingEventStream.

When the circ-padding feature is enabled, the PaddingController is used to tell a set of padding machines about incoming and outgoing traffic to a circuit hop, and the PaddingEventStream is used to decide when to send padding to that hop.

When circ-padding is not enabled, both types are empty, and do nothing.

Padding event semantics

Our events here are fairly tightly coupled to the semantics provided by maybenot.

In brief, maybenot assumes:

• That incoming traffic arrives on a queue, then is decrypted and sorted into “normal” and “padding”.
• That outgoing traffic (normal or padding) is placed onto a queue, and then eventually sent.

For each of these cases, the circuit/tunnnel reactor needs to call an appropriate method on PaddingController to inform each hop’s padding machines about the event.

See the maybenot documentation for more information about when, exactly, each method needs to be invoked.

Design considerations

We expect that a substantial fraction of all circuit hops will require padding in some form. Because of this, we’ve taken some effort to optimize the storage overhead of our padding state.

Re-exports

pub use maybenot_padding::CircuitPadder;

pub use maybenot_padding::CircuitPadderConfig;

pub use maybenot_padding::CircuitPadderConfigError;

Modules

maybenot_padding 🔒

A maybenot-specific backend for padding.