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Reference.org
COMP128
open-in-new
<p>The COMP128 algorithms are implementations of the A3 and A8 functions defined in the <a href="/facts/GSM/Sw8QYaLE">GSM</a> standard. A3 is used to <a href="/facts/Authentication/64y4S69b">authenticate</a> the mobile station to the network. A8 is used to generate the <a href="/facts/Session_key/aDLpKNVQ">session key</a> used by A5 to encrypt the data transmitted between the mobile station and the <a href="/facts/Base_Transceiver_Station/dLDhUMEn">BTS</a>. </p><p>There are three versions of COMP128. They were originally confidential. A partial description of the first version was leaked in 1997 and completed via <a href="/facts/Reverse_engineering/pmJCV7J7">reverse engineering</a>. This led to a full publication in 1998. The second and third versions were obtained via reverse engineering of software which verifies SIM cards compliance. </p>