The A5.1 Decryptor is used to decrypt GSM communications which are encrypted using the GSM A5.1 encryption standard. This equipment is used in conjunction with the Semi-Active or the Passive GSM monitoring system. The A5.1 Decryptor is capable of decrypting A5.1 encrypted GSM communications in real-time. One A5.1 Decryptor can decipher upto 32 sessions simultaneously and can serve the deciphering key to 5 systems in a network.
The system is a single circuit board based on ASIC components and housed inside a ruggedized case along with cooling module. It is powered from compact external power supply. It is controlled by the processing laptop, which is responsible for communication between A5.1 Decryptor and GSM monitoring system.
GSM Interception System sends A5.1 encrypted bit stream to A5.1 Decryptor, usually one encrypted burst derived from forward (downlink) channel. A5.1 decryptor calculates ciphering key Kc and sends it back to the GSM interception system. The GSM interception system implements Kc and decrypts communication.