IMSI Catchers and Mobile Security

the near future. For calls, a new key exchange is generated for every call. For SMS, the initial key
exchange is stored securely on the phone and used through means of a hash-chain.
Figure 9: CryptoPhone Encryption Process
The flagship model, the GSMK CryptoPhone 500, runs on a Samsung Galaxy S3 with a
proprietary OS and costs approximately $3,500 [74]. ESD America estimated that there were
already 30,000 CryptoPhones in the United States and 300,000 worldwide, as of September 2014
[48].
CryptoPhone security is also fortified using a proprietary baseband firewall [75]. The
firewall monitors all connections to the phone’s baseband and reports suspicious activities to the
user, including:
Cell towers that lack an identifying CID
Cell towers with a suspiciously different signal strength
Cell towers operating as expecting or trying to manipulate phones
When the mobile network’s encryption is deactivated
When the cell phone abruptly switches from a 3G or 4G network to a 2G network
When I/O devices are activated through baseband without instructions from OS
When phone makes suspicious connections despite no user activity or ongoing updates
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