Statement from Ricochet-Refresh regarding recent stories in German media about alleged timing attacks affecting our users

Several German media news outlets have run a story about law enforcement agencies allegedly breaking the anonymity provided by Tor and, with it, Ricochet-Refresh. 

We would like to answer some questions on the matter to clarify the facts from the hype. 

1.     Are you aware of cases where Ricochet users were de-anonymised? If so, how?

We are not aware of any cases where users of the current version of Ricochet-Refresh have been de-anonymised. (Including this alleged case, since no evidence of such was provided to us).

The reported attacks occurred 2019-2021, and we have substantially updated the software to improve security since that time. 

Some technical details from our end:

In particular, the vanguards-lite feature was introduced to Ricochet-Refresh in version 3.0.12 in June of 2022, after upgrading to the tor 0.4.7 series. Without being provided with the details of the reported attack, we can not say definitively this feature would have stopped it. However, we do know vanguards were introduced in part to make this general class of attacks more difficult to pull off. Since then, we have continued releasing regular updates which include security updates from our upstream dependencies (including Tor). 

2. What are these ‘timing’ attacks? Could they be applied to anonymous communications? Do they breach the confidentiality of an online conversation?

Again, we have no proven details of the attack and it’s hard to respond to an incident when you can’t see the documentation.  

‘Timing’ attacks have been around for a while, nothing new there. They can in theory unmask the identity of an anonymous end-user, but they do not break open the content of a secret conversation. Generally the attacker in this situation would need vast resources and enormous legal powers to be successful - only the kind that a state could access.

The field of cybersecurity rarely offers absolute guarantees. If you want to be perfectly private, you need to disconnect entirely from the digital world. That’s not a very practical solution for most people.

So you winnow down risk as far as possible. It’s illogical to say ‘because there is some very small risk, we should stop using technology to protect ourselves’. Instead, the best choice is to opt for free, open-source software like Ricochet-Refresh, which by design, gives you enormously more privacy and anonymity than the vast majority of other tools.

3. Is it at all possible for Ricochet-Refresh users to protect themselves against such ‘timing analyses’? If so, how?

Ricochet-Refresh is one of the safest ways to communicate online. The vast majority of people using Ricochet-Refresh do not need to do anything to protect themselves against timing analysis attacks.

In the overwhelming majority of cases, an attacker will not be able to find someone’s identity because they do not have these kinds of very large resources.

As a purely precautionary measure, we suggest end-users who face powerful attackers should limit the number of people to whom they distribute their Ricochet-Refresh ID. In the context of Ricochet-Refresh, most theoretical and practical attacks are only possible if the adversary knows the ID of the target they are attempting to de-anonymise

Note that the content of the message stays secret in the attack scenarios described to us by the journalist who wrote the story.

4. Do you continue to improve Ricochet-Refresh security? 

We do. We provide monthly(ish) Ricochet-Refresh releases when upstream dependencies (e.g. Tor, openssl, qt, etc) publish security updates. Beyond that, we have also been researching and developing an improved back-end which should make ‘timing analysis’ attacks much more difficult by providing the user the ability to control their online visibility to unauthorised peers.

5. Is it safe to continue using Ricochet-Refersh? Why?

Note: Ricochet is not the same as Ricochet-Refresh. Ricochet has been retired because it relies on legacy technology that no longer exists in the Tor Network.

Yes. People should continue using Ricochet-Refresh with a high degree of confidence. It is still one of the most private and secure ways to communicate online.

The protocol is completely peer-to-peer and the client is open-source; there is no account registration, no servers hosting your data, and no centralised organisations or infrastructure to attack. A person’s account data is stored locally on their own computer and their communications are only sent to the intended recipients. These communications are private and secure by default because they are end-to-end encrypted.