Read this outstanding explainer on Dandelion from monerooutreach.org. Really, you won’t find a better one anywhere on the internet. I’ve looked. Answer the questions and post your answers below:
1.Monero node starting the broadcast of a new transaction uses a process called flooding. It is a process it communicates the transaction to all its peers, who in turn communicate to all their peers, and so forth, with some checks to prevent redundant communication. The information travels in all directions over the network like a wave. Some cryptocurrencies, like Bitcoin, randomize the timing of this broadcast, but Monero does not.
2.Dandelion defines a process for finding a proxy node to broadcast, called the anonymity (or stem) phase. And it establishes another process for broadcast, called the spreading (or fluff) phase.
3.There are some minor downsides and limitations. Dandelion++ adds delay to the propagation of transactions. This comes from multiple sources, which are discussed by the Dandelion++ authors [3]. First, the existence of the stem phase adds delay, possibly a few seconds, based on the authors’ analysis and experimental evaluations. Diffusion adds random delays during the fluff phase, typically less than a second. And should the network be subject to a black-hole attack, the confirming wait by the initiator could delay transmission by minutes. These delays are not expected to materially affect the network. Also, Dandelion++ does not encrypt the P2P packets, and does not protect against ISP/VPN-level spying—for this, you can use Tor.
Flooding is when a node communicates the transaction to all its peers, who in turn communicate to all their peers, and so forth, with some checks to prevent redundant communication. The information travels in all directions over the network like a wave. Some cryptocurrencies, like Bitcoin, randomize the timing of this broadcast, but Monero does not.
◦ Anonymity (or stem) phase - seeking out a proxy node along a special linear search path
◦ The Spreading (or fluff) phase – After seeking out a proxy node, then from this proxy node spreading the information rapidly and symmetrically
Dandelion++ tweaks Dandelion to resist large-scale rule-breaking deanonymization attacks.
In the new stem phase, to implement dynamic connectivity, it proceeds in discreet intervals, called epochs. Each node switches epoch independently, typically every few minutes. With each new epoch, a node picks two new relay connections at random from its outbound connections. Then whenever the node creates its own transaction it sends it over one of these two relays, always making the same choice for a given epoch. And whenever it gets a transaction from another node for forwarding during stem phase, if it is a relayer (more on this below), it sends it out randomly over one of the two relays.
What is ‘flooding’?
A propagation technic of transactions in the P2P network.
What are the two phases of a Dandelion broadcast and what happens in each phase?
“Anonymity or stem phase” to find a proxy node to broadcast and “spreading or fluff phase” to broadcast the transaction, using different set of peers in each phase and changing connection set with time in the “anonimity phase”.
What potential weakness of Dandelion does Dandelion++ aim to address?
Large scale rule breaking deanonymization attacks: bootnet with spy nodes distributed through the network not following the rules and using all available information (time, addresses of senders and receivers,…).
Under the Dandelion++ protocol, what are the two ways to transition from the ‘stem’ phase to the ‘fluff’ phase?
With a new epoch, where the nodes classifies itself as relayer (stem) o difusser (fluff)
If a time threshold passes after relaying a transaction during stem phase and not receiving the same transaction back during a fluff phase, in this case the node starts its own fluff phase.
What is ‘flooding’?
Is the process used from Monero nodes starting a broadcast.Is called flooding because propagate like a wave, whit the node peers communicating to their peers, that consequently communicate it to their peers and so going.
What are the two phases of a Dandelion broadcast and what happens in each phase?
STEM phase is called the process of looking for a proxy node to broadcast.
FLUFF phase is the process of broadcasting (or spreading) to the network.
What potential weakness of Dandelion does Dandelion++ aim to address?
Is just a refined version of the same thing tuned to resist large-scale rule-breaking deanonymization attacks.
Under the Dandelion++ protocol, what are the two ways to transition from the ‘stem’ phase to the ‘fluff’ phase?
Switching the epoch (where the node classificate itself relayer/diffuser) or trough “fail-safe" mechanism(starting his own fluff when, at process started, a Tx doesn’t come back after a set time threshold)
What is ‘flooding’?
Is a process of a monero node starting to broadcast a new transaction.
What are the two phases of a Dandelion broadcast and what happens in each phase?
Finding a proxy node to broadcast is called the anonymity (or stem) phase. And it establishes another process for broadcast, called the spreading (or fluff) phase.
What potential weakness of Dandelion does Dandelion++ aim to address?
Dandelion++ tweaks Dandelion to resist large-scale rule-breaking deanonymization attacks.
Under the Dandelion++ protocol, what are the two ways to transition from the ‘stem’ phase to the ‘fluff’ phase?
For each epoch, a node classifies itself as either a relayer or a diffuser. The mode is determined at random at the start of the epoch. If a node is a diffuser, whenever it is given a transaction to relay as stem phase, it instead broadcasts it using diffusion, thereby starting the fluff phase.
What is ‘flooding’?
Flooding means broadcasting a transaction from a node to all of its peers who again broadcast to other peers and so on.
What are the two phases of a Dandelion broadcast and what happens in each phase?
What potential weakness of Dandelion does Dandelion++ aim to address?
Some adversaries might not follow the rules of Dandelion to deanonymize the users.
Under the Dandelion++ protocol, what are the two ways to transition from the ‘stem’ phase to the ‘fluff’ phase?
Dynamic connectivity: Nodes switch epochs independently, and in each epoch the node chooses two relays randomly, and when the node forwards a transaction, it sends it to one of these two relays randomly
Fail-safe mechanism: Each node that relays a transaction during stem phase starts a timer for that transaction. If a time threshold passes without the node receiving the same transaction back during a fluff phase, it starts its own fluff phase.
1- Flooding communicates the transaction to all its peers, who in turn communicate to all their peers, and so forth, with some checks to prevent redundant communication. The information travels in all directions over the network like a wave. Some cryptocurrencies, like Bitcoin, randomize the timing of this broadcast, but Monero does not.
2- Dandelion defines a process for finding a proxy node to broadcast, called the anonymity (or stem) phase. And it establishes another process for broadcast, called the spreading (or fluff) phase. In general, the two phases use different sets of peer connections with the important difference that the anonymity phase connection set changes with time.
3- Dandelion++ tweaks Dandelion to resist large-scale rule-breaking deanonymization attacks.
4-“Epochs switching” method or through the “fail-safe mechanism”.
I do like to read and study from good articles, and thanks for great selection and nice learning order of them all, but, I would suggest additional/more examples of ‘media’ presentations on the course, even if there where no time to release why not use some good ones are available ‘open’ already out there on the internet …
some other ‘verbal’ explanations about Dandelion :
from Andreas Antonopoulos:
Method of broadcasting transaction in Monero
Stem: Transaction is tunelled to a proxy node.
Fluff: Transaction is then broadcasted to peers like adandelion.
Protection against large-scale rule-breaking deanonymization attacks with large fraction of nodes being active (dishonest).
If the node is a relayer it sends it randomly to 1 of 2 relays,
If the node is a diffuser, it broadcasts transaction, thus starting the fluff phase.
What is ‘flooding’?
The node communicates the transaction to all its peers, who in turn communicate to all their peers, and so forth, with some checks to prevent redundant communication. The information travels in all directions over the network like a wave.
What are the two phases of a Dandelion broadcast and what happens in each phase?
First seeking out a proxy node along a special linear search path, then from this proxy node spreading the information rapidly and symmetrically.
What potential weakness of Dandelion does Dandelion++ aim to address?
Some nodes may not follow the rules of the network. Some honest nodes may not run Dandelion.
Under the Dandelion++ protocol, what are the two ways to transition from the ‘stem’ phase to the ‘fluff’ phase?
In the new stem phase, to implement dynamic connectivity, it proceeds in discreet intervals, called epochs. Each node switches epoch independently, typically every few minutes. With each new epoch, a node picks two new relay connections at random from its outbound connections.
The fluff phase in Dandelion++ uses diffusion, the flooding process where the timing of the communications are random to make it harder for spy nodes to locate the source. Once a transaction has started the diffusion process it continues to propagate using diffusion, never going back to the stem phase.
A node broadcasts to all the peers it knows then each of those peers broadcast to all their peers, etc.
Dandelion requires nodes to follow the Dandelion rules, but not all nodes may be using Dandelion. The ++ version is resistant to large scale rule breaking attacks.
Thanks for the suggestion, it’s a good idea! We can easily add some ‘further research’ links to podcasts or other YouTube videos.