server to the network. As the number of servers and their addresses change frequently, client programs update their server lists regularly. Features Hash identification Files on the eDonkey network are uniquely identified using MD4 root hash of an MD4 hash list of the file. This treats files with identical content but different names as the same, and files with different contents but same name as different. Files are divided in full chunks of 9,728,000 bytes (9500 KiB) plus a remainder chunk, and a separate 128-bit MD4 checksum is computed for each. That way, if a transmission error is detected, only one chunk is corrupted instead of the whole file. Furthermore, valid downloaded chunks are available for sharing before the rest of the file is downloaded, speeding up the distribution of large files throughout the network. A file's identification checksum is computed by concatenating the chunks' MD4 checksums in order and hashing the result. In cryptographic terms, the list of MD4 checksums is a hash list, and the file identification checksum is the root hash, also called top hash or master hash. It is possible for a malicious user to create two different chunks with the same checksum due to MD4 being vulnerable to collision attacks. Search The eDonkey network supports searching of files by name and a number of secondary characteristics such as size, extension, bitrate, etc. The Lugdunum versions of eserver (eDonkey server software) support complex boolean searches like 'one AND two AND (three OR four) AND ("five four three" OR "two one") NOT seven'. To ease file searching, some websites list the checksums of sought-after files in the form of an eD2k link. Some of these websites also have lists of active servers for users to update. History In 2004, the eDonkey network overtook FastTrack to become the most widely used file sharing network on the Internet. While figures vary from hour to hour, it is believed, as of mid-2005, to host on average approximately two to three million users sharing 500 million to two billion files via 100 to 200 servers. The network’s most popular server was at one time Razorback2, which usually hosted about one million users. Sometime around February 21, 2006, the Razorback2 servers were raided and seized by the Federal Belgian Police. DonkeyServer No1 and DonkeyServer No2 currently combine for over one and a half million users. However, around July 16, 2007, both servers