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@ -21,8 +21,8 @@ instead of disseminating messages as per usual relay operation.
## Background and Motivation ## Background and Motivation
[Waku Relay](https://rfc.vac.dev/waku/standards/core/11/relay), offers privacy, pseudonymity, and a first layer of anonymity protection by design. [Waku Relay](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/11/relay.md), offers privacy, pseudonymity, and a first layer of anonymity protection by design.
Being a modular protocol family [Waku v2](https://rfc.vac.dev/waku/standards/core/10/waku2) Being a modular protocol family [Waku v2](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/10/waku2.md)
offers features that inherently carry trade-offs as separate building blocks. offers features that inherently carry trade-offs as separate building blocks.
Anonymity protection is such a feature. Anonymity protection is such a feature.
The [Anonymity Trilemma](https://freedom.cs.purdue.edu/projects/trilemma.html) The [Anonymity Trilemma](https://freedom.cs.purdue.edu/projects/trilemma.html)
@ -37,7 +37,7 @@ and [Dandelion++](https://arxiv.org/abs/1805.11060).
Dandelion is a message spreading method, which, compared to other methods, Dandelion is a message spreading method, which, compared to other methods,
increases the uncertainty of an attacker when trying to link messages to senders. increases the uncertainty of an attacker when trying to link messages to senders.
Libp2p gossipsub aims at spanning a [d-regular graph](https://en.wikipedia.org/wiki/Regular_graph) topology, with d=6 as the [default value](https://rfc.vac.dev/spec/29/#gossipsub-v10-parameters). Libp2p gossipsub aims at spanning a [d-regular graph](https://en.wikipedia.org/wiki/Regular_graph) topology, with d=6 as the [default value](https://github.com/vacp2p/rfc-index/blob/main/waku/informational/29/config.md/#gossipsub-v10-parameters).
Messages are forwarded within this (expected) symmetric topology, Messages are forwarded within this (expected) symmetric topology,
which reduces uncertainty when trying to link messages to senders. which reduces uncertainty when trying to link messages to senders.
Dandelion breaks this symmetry by subdividing message spreading into a "stem" and a "fluff" phase. Dandelion breaks this symmetry by subdividing message spreading into a "stem" and a "fluff" phase.
@ -61,11 +61,11 @@ Further information on Waku anonymity may be found in our [Waku Privacy and Anon
## Theory and Functioning ## Theory and Functioning
WAKU2-DANDELION can be seen as an anonymity enhancing add-on to [Waku Relay](https://rfc.vac.dev/waku/standards/core/11/relay) message dissemination, WAKU2-DANDELION can be seen as an anonymity enhancing add-on to [Waku Relay](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/11/relay.md) message dissemination,
which is based on [libp2p gossipsub](https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/README.md). which is based on [libp2p gossipsub](https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/README.md).
WAKU2-DANDELION subdivides message dissemination into a "stem" and a "fluff" phase. WAKU2-DANDELION subdivides message dissemination into a "stem" and a "fluff" phase.
This specification is mainly concerned with specifying the stem phase. This specification is mainly concerned with specifying the stem phase.
The fluff phase corresponds to [Waku Relay](https://rfc.vac.dev/waku/standards/core/11/relay), The fluff phase corresponds to [Waku Relay](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/11/relay.md),
with optional fluff phase augmentations such as random delays. with optional fluff phase augmentations such as random delays.
Adding random delay in the fluff phase further reduces symmetry in dissemination patterns and Adding random delay in the fluff phase further reduces symmetry in dissemination patterns and
introduces more uncertainty for the attacker. introduces more uncertainty for the attacker.
@ -92,7 +92,7 @@ are always sent as stem messages.
The stem phase can be seen as a different protocol, and messages are introduced into Waku Relay, and by extension gossipsub, The stem phase can be seen as a different protocol, and messages are introduced into Waku Relay, and by extension gossipsub,
once they arrive at a node in fluff state for the first time. once they arrive at a node in fluff state for the first time.
WAKU2-DANDELION uses [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush) as the protocol for relaying stem messages. WAKU2-DANDELION uses [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md) as the protocol for relaying stem messages.
There are no negative effects on gossipsub peer scoring, There are no negative effects on gossipsub peer scoring,
because Dandelion nodes in _stem state_ still normally relay Waku Relay (gossipsub) messages. because Dandelion nodes in _stem state_ still normally relay Waku Relay (gossipsub) messages.
@ -116,16 +116,16 @@ corresponding to 10 minute epochs.
On entering stem state, On entering stem state,
nodes supporting WAKU2-DANDELION MUST randomly select two nodes for each pubsub topic from the respective gossipsub mesh node set. nodes supporting WAKU2-DANDELION MUST randomly select two nodes for each pubsub topic from the respective gossipsub mesh node set.
These nodes are referred to as stem relays. These nodes are referred to as stem relays.
Stem relays MUST support [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush). Stem relays MUST support [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md).
If a chosen peer does not support [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush), If a chosen peer does not support [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md),
the node SHOULD switch to fluff state. the node SHOULD switch to fluff state.
(We may update this strategy in future versions of this document.) (We may update this strategy in future versions of this document.)
Further, the node establishes a map that maps each incoming stem connection Further, the node establishes a map that maps each incoming stem connection
to one of its stem relays chosen at random (but fixed per epoch). to one of its stem relays chosen at random (but fixed per epoch).
Incoming stem connections are identified by the [Peer IDs](https://docs.libp2p.io/concepts/peers/#peer-id/) Incoming stem connections are identified by the [Peer IDs](https://docs.libp2p.io/concepts/peers/#peer-id/)
of peers the node receives [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush) messages from. of peers the node receives [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md) messages from.
Incoming [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush) connections from peers that do not support WAKU2-DANDELION are identified and mapped in the same way. Incoming [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md) connections from peers that do not support WAKU2-DANDELION are identified and mapped in the same way.
This makes the protocol simpler, increases the anonymity set, and offers Dandelion anonymity properties to such peers, too. This makes the protocol simpler, increases the anonymity set, and offers Dandelion anonymity properties to such peers, too.
The node itself is mapped in the same way, so that all messages originated by the node are relayed via a per-epoch-fixed Dandelion relay, too. The node itself is mapped in the same way, so that all messages originated by the node are relayed via a per-epoch-fixed Dandelion relay, too.
@ -133,7 +133,7 @@ The node itself is mapped in the same way, so that all messages originated by th
While in stem state, nodes MUST relay stem messages to the respective stem relay. While in stem state, nodes MUST relay stem messages to the respective stem relay.
Received fluff messages MUST be relayed as specified in the fluff state section. Received fluff messages MUST be relayed as specified in the fluff state section.
The stem protocol ([19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush)) is independent of the fluff protocol ([Waku Relay](https://rfc.vac.dev/waku/standards/core/11/relay)). The stem protocol ([19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md)) is independent of the fluff protocol ([Waku Relay](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/11/relay.md)).
While in stem state, nodes MUST NOT gossip about stem messages, While in stem state, nodes MUST NOT gossip about stem messages,
and MUST NOT send control messages related to stem messages. and MUST NOT send control messages related to stem messages.
(An existing gossipsub implementation does _not_ have to be adjusted to not send gossip about stem messages, (An existing gossipsub implementation does _not_ have to be adjusted to not send gossip about stem messages,
@ -161,7 +161,7 @@ this regular forwarding already comprises random delays.
## Implementation Notes ## Implementation Notes
Handling of the WAKU2-DANDELION stem phase can be implemented as an extension to an existing [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush) implementation. Handling of the WAKU2-DANDELION stem phase can be implemented as an extension to an existing [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md) implementation.
Fluff phase augmentations might alter gossipsub message dissemination (e.g. adding random delays). Fluff phase augmentations might alter gossipsub message dissemination (e.g. adding random delays).
If this is the case, they have to be implemented on the libp2p gossipsub layer. If this is the case, they have to be implemented on the libp2p gossipsub layer.
@ -197,7 +197,7 @@ WAKU2-DANDELION does not protect against targeted deanonymization attacks.
Stem relays receiving messages can either be in stem state or in fluff state themselves. Stem relays receiving messages can either be in stem state or in fluff state themselves.
They might also not support WAKU2-DANDELION, They might also not support WAKU2-DANDELION,
and interpret the message as classical [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush), and interpret the message as classical [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md),
which effectively makes them act as fluff state relays. which effectively makes them act as fluff state relays.
While such peers lower the overall anonymity properties, While such peers lower the overall anonymity properties,
the [Dandelion++ paper](https://arxiv.org/abs/1805.11060) the [Dandelion++ paper](https://arxiv.org/abs/1805.11060)
@ -234,9 +234,9 @@ We will quantify the resulting loss of anonymity in future versions of this docu
#### Stem Relay Selection #### Stem Relay Selection
In its current version, WAKU2-DANDELION nodes default to fluff state In its current version, WAKU2-DANDELION nodes default to fluff state
if the random stem relay selection yields at least one peer that does not support [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush) (which is the stem protocol used in WAKU2-DANDELION. if the random stem relay selection yields at least one peer that does not support [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md) (which is the stem protocol used in WAKU2-DANDELION.
If nodes would reselect peers until they find peers supporting [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush), If nodes would reselect peers until they find peers supporting [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md),
malicious nodes would get an advantage if a significant number of honest nodes would not support [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush). malicious nodes would get an advantage if a significant number of honest nodes would not support [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md).
Even though this causes messages to enter fluff phase earlier, Even though this causes messages to enter fluff phase earlier,
we choose the trade-off in favour of protocol stability and sacrifice a bit of anonymity. we choose the trade-off in favour of protocol stability and sacrifice a bit of anonymity.
(We will look into improving this in future versions of this document.) (We will look into improving this in future versions of this document.)
@ -254,7 +254,7 @@ We plan to add a separate fluff augmentation specification that will introduce r
Optimal delay times depend on the message frequency and patterns. Optimal delay times depend on the message frequency and patterns.
This delay fluff augmentation specification will be oblivious to the actual message content, This delay fluff augmentation specification will be oblivious to the actual message content,
because Waku Dandelion specifications add anonymity on the routing layer. because Waku Dandelion specifications add anonymity on the routing layer.
Still, it is important to note that [Waku2 messages](https://rfc.vac.dev/waku/standards/core/14/message/#payloads) (in their current version) carry an originator timestamp, Still, it is important to note that [Waku2 messages](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/14/message.md/#payloads) (in their current version) carry an originator timestamp,
which works against fluff phase random delays. which works against fluff phase random delays.
An analysis of the benefits of this timestamp versus anonymity risks is on our roadmap. An analysis of the benefits of this timestamp versus anonymity risks is on our roadmap.
@ -267,14 +267,14 @@ Note: Introducing random delays can have a negative effect on
#### Stem Flag #### Stem Flag
While WAKU2-DANDELION without fluff augmentation does not effect Waku Relay nodes, While WAKU2-DANDELION without fluff augmentation does not effect Waku Relay nodes,
messages sent by nodes that only support [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush) might be routed through a Dandelion stem without them knowing. messages sent by nodes that only support [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md) might be routed through a Dandelion stem without them knowing.
While this improves anonymity, as discussed above, it also introduces additional latency and lightpush nodes cannot opt out of this. While this improves anonymity, as discussed above, it also introduces additional latency and lightpush nodes cannot opt out of this.
In future versions of this specification we might In future versions of this specification we might
- add a flag to [14/WAKU2-MESSAGE](https://rfc.vac.dev/waku/standards/core/14/message) indicating a message should be routed over a Dandelion stem (opt-in), or - add a flag to [14/WAKU2-MESSAGE](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/14/message.md) indicating a message should be routed over a Dandelion stem (opt-in), or
- add a flag to [14/WAKU2-MESSAGE](https://rfc.vac.dev/waku/standards/core/14/message) indicating a message should _not_ be routed over a Dandelion stem (opt-out), or - add a flag to [14/WAKU2-MESSAGE](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/14/message.md) indicating a message should _not_ be routed over a Dandelion stem (opt-out), or
- introducing a fork of [19/WAKU2-LIGHTPUSH](https://rfc.vac.dev/waku/standards/core/19/lightpush) exclusively used for Dandelion stem. - introducing a fork of [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md) exclusively used for Dandelion stem.
In the current version, we decided against these options in favour of a simpler protocol and an increased anonymity set. In the current version, we decided against these options in favour of a simpler protocol and an increased anonymity set.
@ -287,11 +287,13 @@ Copyright and related rights waived via [CC0](https://creativecommons.org/public
- [Dandelion](https://arxiv.org/abs/1701.04439) - [Dandelion](https://arxiv.org/abs/1701.04439)
- [Dandelion++](https://arxiv.org/abs/1805.11060) - [Dandelion++](https://arxiv.org/abs/1805.11060)
- [multi-node (botnet) attacker model](../../informational/adversarial-models.md/#multi-node) - [multi-node (botnet) attacker model](../../informational/adversarial-models.md/#multi-node)
- [Waku Relay](https://rfc.vac.dev/waku/standards/core/11/relay) - [Waku Relay](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/11/relay.md)
- [Waku v2](https://rfc.vac.dev/waku/standards/core/10/waku2) - [Waku v2](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/10/waku2.md)
- [d-regular graph](https://en.wikipedia.org/wiki/Regular_graph) - [d-regular graph](https://en.wikipedia.org/wiki/Regular_graph)
- [Anonymity Trilemma](https://freedom.cs.purdue.edu/projects/trilemma.html) - [Anonymity Trilemma](https://freedom.cs.purdue.edu/projects/trilemma.html)
- [Waku Privacy and Anonymity Analysis](https://vac.dev/wakuv2-relay-anon). - [Waku Privacy and Anonymity Analysis](https://vac.dev/wakuv2-relay-anon).
- [On the Anonymity of Peer-To-Peer Network Anonymity Schemes Used by Cryptocurrencies](https://arxiv.org/pdf/2201.11860.pdf) - [On the Anonymity of Peer-To-Peer Network Anonymity Schemes Used by Cryptocurrencies](https://arxiv.org/pdf/2201.11860.pdf)
- [Adversarial Models](../../informational/adversarial-models.md) - [Adversarial Models](../../informational/adversarial-models.md)
- [14/WAKU2-MESSAGE](https://rfc.vac.dev/waku/standards/core/14/message) - [14/WAKU2-MESSAGE](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/14/message.md)
- [29/WAKU-CONFIG](https://github.com/vacp2p/rfc-index/blob/main/waku/informational/29/config.md)
- [19/WAKU2-LIGHTPUSH](https://github.com/vacp2p/rfc-index/blob/main/waku/standards/core/19/lightpush.md)