upgrades and fixes, the Battle.net service updates the customer's game before allowing the game to play in Battle.net mode.
B. Technology of the Battle.net Service
Blizzard's games are shipped to customers on CD-ROM disks. Except for the game "Diablo," each authorized version of a Blizzard game comes with a "CD Key," a unique sequence of alphanumeric characters that is printed on a sticker attached to the case in which the CD-ROM was packaged. The user of the game must input the CD Key into his or her computer when installing the game, and it is subsequently stored on the computer for use in logging on to the Battle.net service. The Battle.net service prohibits use of unauthorized or pirated copies of Blizzard games with the Battle.net service.
To log on to theBattle.net service and access Battle.net mode, the game initiates a authentication sequence or "secret handshake" between the game and Battle.net server. First, the game and Battle.net server exchange random numbers (one provided by the game and one provided by the server). The game then takes the random numbers, as well as information from the CD Key, and calculates an encrypted alphanumeric sequence which is sent to the Battle.net server. The game performs this encryption to prevent individuals from stealing the game's CD Key when it is transmitted over the Internet to a Battle.net server. The Battle.net server receives the alphanumeric sequence sent by the game, along with other information sent by the game, and uses this data to determine whether the CD Key information sent by the game