definition of tor

The Onion Router (Tor) is a decentralized network communication system that protects user privacy and anonymity. It works by encrypting and routing user network traffic through multiple nodes in layers, where each node can only see the traffic's source and next destination without knowing the complete communication path. This design resembles the layered structure of an onion, hence the name "Onion Router." The Tor network not only allows users to anonymously access internet resources but also supports so-called "dark web" services that are only accessible within the Tor network, providing enhanced privacy protection.

Background: The Origin of Tor

The onion routing technology was initially developed by the U.S. Naval Research Laboratory in the mid-1990s to protect U.S. intelligence communications. The first version of the Tor software was released in 2002, and in 2004, the project became open-source, maintained and developed by the non-profit organization The Tor Project. Originally designed to secure government communications, it gradually expanded to become a tool for protecting internet users' privacy rights and freedom of speech globally.

With the increase in internet surveillance and data collection, the Tor network has become an important tool for journalists, activists, ordinary citizens, and even law enforcement agencies to protect sensitive communications. Especially in countries where freedom of speech is restricted, Tor has become one of the key technologies for bypassing national internet censorship.

Work Mechanism: How Tor Works

The working principle of onion routing is based on multi-layer encryption and a distributed relay network:

1. Multi-layer encryption: When a user sends data through Tor, the Tor client first randomly selects three relay nodes in the network (entry node, middle node, and exit node).

2. Encrypted path: The client adds three layers of encryption to the data, each corresponding to a node's public key. Each node can only decrypt its corresponding layer to get the information of the next destination.

3. Data transmission process: The entry node receives the traffic and removes the first layer of encryption, sending the data to the middle node; the middle node removes the second layer of encryption, forwarding the data to the exit node; the exit node removes the final layer of encryption, sending the original request to the target website.

4. Return path: Response data returns along the same path but in the opposite direction, with each node adding a layer of encryption during forwarding.

5. Regular path changes: To enhance security, the Tor client changes its path approximately every 10 minutes.

Risks and Challenges: Limitations of Tor

Despite providing powerful privacy protection for users, Tor still faces several challenges:

1. Speed limitations: Multi-layer encryption and multiple data relays result in significantly reduced network connection speeds, making it unsuitable for high-bandwidth activities like large file transfers or streaming media.

2. Exit node risks: Exit nodes can see unencrypted data sent to target websites. If users access websites not using HTTPS, malicious exit nodes may monitor their activities.

3. Traffic analysis attacks: Powerful adversaries can break user anonymity by simultaneously monitoring the network's entry and exit traffic and performing time correlation analysis.

4. Misuse issues: Due to its anonymity features, the Tor network is sometimes used for illegal activities, leading to negative perceptions and legal challenges.

5. Censorship and blocking: Some countries and organizations attempt to block access to the Tor network. To counter this, the Tor Project has developed anti-censorship measures such as bridge technology.

The value of onion routing technology lies in providing infrastructure for anonymous communication on the internet. Despite these challenges, it remains an important tool for users who need to protect their privacy, avoid surveillance, or communicate freely in controlled environments. In the cryptocurrency field, many privacy coin projects have also borrowed concepts from onion routing to enhance transaction privacy and anonymity.