The Tor project have recently announced that it is implementing a new Counter Galois Onion (CGO) relay encryption algorithm. Cryptographers Jean Paul Degabriele, Alessandro Melloni, Jean Pierre Munch and Martijn Stam has been designed CGO for years.

According to the Tor project, Iran is in the top 3 countries with the highest number of Tor users. Many Iranians use Tor (also known as the onion router) due to government censorship and internet restrictions and shutdowns.

Tor has said that these upcoming changes will improve security and encryption by replacing the old tor1 relay encryption algorithm with the new design CGO.

What are the reasons for the change?

• To make the network more resilient against modern traffic interception attacks that may compromise data security and undermine Tor user anonymity.
• It will help defend users against a broader class of online attackers.
• If anyone tries to tamper with any part of encrypted data, the entire message and future messages will become unrecoverable.
• Stronger authentication – CGO will replace the 4 byte SHA-1 digest used in Tor1 with a 16 byte authenticator.

Issues with the previous tor1 design:

• Tagging attacks – these attacks enable adversaries to trace traffic by modifying it in one place on the network, and observing predicatble changes in anothjer. This is the most important attack that is being solved with CGO.
• Weaker security -Tor1 reused the same AES key throughout a circuit’s lifetime whereas CGO updated keys after each cell.

When will these changes take place?

CGO has already been implemented in Arti, the Rust-based version of Tor and it is being integrated into the C version of Tor relay.

This upgrade represents a significant advancement in Tor’s cryptographic capabilities and will provide users with enhanced privacy and security.