In 2015 the FBI wanted to hack the iPhone of a terrorist, highlighting the Crypto Wars: the authorities have fight for more power, and the defenders of computer privacy become increasingly good at securing information against unwanted spies.
But privacy on the internet is not only important for terrorists, but also highly valued by the ‘normal users’. A lot of websites already help people to encrypt their messages by giving every visiting computer a unique key. These keys are hard to retrieve and hard to crack, causing a lot of hackers to stay clear. But in spite of the encryption, users are still traceable, and thus never really anonymous. This is because the destination of a message has to stay readable in order for it to reach its destination.
In 1981 David Chaum came up with an idea to solve this problem: Tor. Tor consists of a network of computers, enabled by volunteers from around the world. If a user contacts someone, Tor randomly chooses three of these computers called nodes. The sender encrypts each message three times, before it sends the message to the first computer. This computer peels off the outer encryption layer and sends the message on to the second computer. This is process is continued until the message reaches its destination. If spyware were to hack one of the nodes, it could find out either the sender or the recipient, but never both. In order to know both sides of the communication, all nodes should be hacked, and since these are three random computers out of a huge network, this is an almost impossible job. But, also this system has its downsides: it is quite slow, the nodes are normal computers (i.e. not super secure), the message can still be traced by matching the times messages are sent and received and the encryption doesn’t change the length of the sent message, causing it to be recognizable.
To correct these downsides, Chaum came up with the idea for cMix-network in 2016. In the cMix-network, the nodes are exchanged for around ten servers in datacenters, all in different countries with good privacy regulations. The differences with Tor are:
- The nodes are always the same servers, used in the same order, but hacking the servers is a lot harder than hacking one of the computers that is used for Tor;
- The sender must complement its message to meet the standard length, causing it to be unrecognizable;
- The message has 10 encryption layers instead of 3;
- The message is sent to the network where it is coupled with a standard amount of other messages, mixing the order of messages, to form a batch. This means that the messages have to wait for some amount milliseconds, making it harder to match the times messages are sent and received;
- The system is faster because the servers make encryption codes in advance, when there is little traffic to keep them busy.
Because of the Crypto Wars, Chaum also came up with PrivaTegrity, in which the anonymity of criminals can be taken away. This network consists of nine servers in different countries. If the administrators of these servers unanimously decide that a person must be traced, they can do so, and all the servers will communicate with each other to reconstruct the complete path a message has traveled. Which problems do you see with this idea? Would it be a good idea to use a system like PrivaTegrity? Or should we keep using systems like Tor and cMix?
Sources:
Können, T. (2016). Gemixte berichten. De ingenieur. 128 (7), 26-28.
Chaum, D. (2016). cMix: Anonymization by High-Performance Scalable Mixing. 1-16.
