Cryptographic key protection against FROST for mobile devices

With the flourish of applications based on the internet of things and cloud computing, privacy issues have been attracting a lot of attentions. Although the increasing use of full disk encryption (FDE) significantly hamper privacy leakage and digital forensics, cold boot attacks have thwarted FDE since forensic recovery of scrambled telephones (FROST), a forensic tool, is proposed. The cryptographic keys which are stored in the mobile devices are inclined to be obtained by FROST. Recent research results have shown CPU-bound encryption methods to resist FROST. However, these methods performs AES encryption solely on CPU registers, whose advantage comes at the cost of encryption speed. This paper, therefore, presents a cryptographic key protection scheme for android devices which prevents FROST from acquiring the key of AES by changing storage location of the key in memory. The storage location of the key is switched to the fixed position where command line parameters will be stored when android boots. Therefore, the key will be covered by command line parameters while the system reboots, which negates FROST from obtaining the key. Compared with the popular CPU-bound encryption methods, our method has less impact on encryption efficiency and employs no additional storage resources.