It is regarded as a design defect that high I/O performance is not compatible to high security in the file encryption mechanism used nowadays in Android platform. To solve this problem
we presented a new transparent file encryption mechanism based on the mapping chart encryption and physical block encryption. It applies 10-round AES-128 block cipher algorithm to the mapping chart encryption and applies revised 7-round AES-128 block cipher algorithm to physical block encryption
which contributes to the balance between I/O performance and high security. Then we performed cryptanalysis and proved that the cipher strength of our mechanism is not lower than Android's. In addition
we have conducted I/O performance theoretical analysis and concluded that the I/O performance of this mechanism is higher than Android's. Moreover
we also performed 108 I/O performance tests in different test conditions on Google Nexus 4 smart phone. The result of these tests not only verifies the conclusion proved by I/O performance analysis
but also shows that the I/O writing performance of our mechanism is 13.12% higher than Android's and the I/O reading performance is 16.16% higher than that of Android system.
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