traffic analysis | Tor Blog

New low cost traffic analysis attacks and mitigations

Recently, Tobias Pulls and Rasmus Dahlberg published a paper entitled Website Fingerprinting with Website Oracles.

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A Critique of Website Traffic Fingerprinting Attacks

Website traffic fingerprinting is an attack where the adversary attempts to recognize the encrypted traffic patterns of specific web pages without using any other information.

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Experimental Defense for Website Traffic Fingerprinting

Updated 09/05/2011: Add link to actual

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Recent Updates

Snowflake moving to stable in Tor Browser 10.5

We're excited to announce that Snowflake will be shipped as one of the default bridge options with stable versions of Tor Browser later this month.

New Release: Tor Browser 10.0.18

Tor Browser 10.0.18 is now available from the Tor Browser download page and also from our

Internet Freedom, Privacy, & LGBTQIA+ Human Rights

Every June, we recognize Pride month because internet freedom and the human rights of LGBTQIA+ people go hand in hand.

New stable security releases: 0.3.5.15, 0.4.4.9, 0.4.5.9, 0.4.6.5

After months of work, we have a new stable release series! If you build Tor from source, you can download the source code for 0.4.6.5 on the download page. Packages should be available within the next several weeks, with a new Tor Browser around the end of the week.

Because this release includes security fixes, we are also releasing updates for our other supported releases. You can find their source at https://dist.torproject.org:

0.3.5.15 (gpg signature) (ChangeLog)
0.4.4.9 (gpg signature) (ChangeLog) [Note that 0.4.4.9 hits end-of-life tomorrow; this is the last supported 0.4.4.9 release.]
0.4.5.9 (gpg signature) (ChangeLog)

Tor 0.4.6.5 is the first stable release in its series. The 0.4.6.x series includes numerous features and bugfixes, including a significant improvement to our circuit timeout algorithm that should improve observed client performance, and a way for relays to report when they are overloaded.

This release also includes security fixes for several security issues, including a denial-of-service attack against onion service clients, and another denial-of-service attack against relays. Everybody should upgrade to one of 0.3.5.15, 0.4.4.9, 0.4.5.9, or 0.4.6.5.

Below are the changes since 0.4.5.8. For a list of changes since 0.4.6.4-rc, see the ChangeLog file.

Changes in version 0.4.6.5 - 2021-06-14

Major bugfixes (security):
- Don't allow relays to spoof RELAY_END or RELAY_RESOLVED cell on half-closed streams. Previously, clients failed to validate which hop sent these cells: this would allow a relay on a circuit to end a stream that wasn't actually built with it. Fixes bug 40389; bugfix on 0.3.5.1-alpha. This issue is also tracked as TROVE-2021- 003 and CVE-2021-34548.
Major bugfixes (security, defense-in-depth):
- Detect more failure conditions from the OpenSSL RNG code. Previously, we would detect errors from a missing RNG implementation, but not failures from the RNG code itself. Fortunately, it appears those failures do not happen in practice when Tor is using OpenSSL's default RNG implementation. Fixes bug 40390; bugfix on 0.2.8.1-alpha. This issue is also tracked as TROVE-2021-004. Reported by Jann Horn at Google's Project Zero.