2022-01-16 21:30:01 +00:00
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= GSM =
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GSM or the global system for mobile communications is a standard developed to
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standardize cellphones and their communication and infrastructure.
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2022-01-16 21:45:01 +00:00
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GSM handsets derive the baudrate from very very accurate clocks on the base
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station.
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== Bands ==
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2022-01-17 04:00:01 +00:00
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GSM occupies
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2022-01-16 21:45:01 +00:00
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* 850 (USA)
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* 900 (europe)
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* 1800 (europe)
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* 1900 (USA)
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*NOTE* GSM-900 uses 880-914mhz
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The 33cm ham band is 902-928mhz. Therefore, for 902-914 we can transmit legally
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as a eurpean tower.
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This band is also the ISM (industrial scientific medical) band. Most devices on
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this band are low power and low utilisation.
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2022-01-16 21:30:01 +00:00
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== IMSI ==
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International Mobile Subscriber Identity is a way for devices to id themselves
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on a GSM network. An IMSI is a secret key that is stored on the SIM card.
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=== IMSI catcher ===
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A spoofed GSM tower. In GSM the base station (tower) picks all settings
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including Tx power, Rx gain, encryption, etc
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2022-01-16 21:45:01 +00:00
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When the tower tells the handset to disable encryption (A5/0), and handset
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_should_ tell user about this. Hoever every manufacturer disables this
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