Taejoo Chang

New acquisition method based on firmware update protocols for Android smartphones

Android remains the dominant OS in the smartphone market even though the iOS share of the market increased during the iPhone 6 release period. As various types of Android smartphones are being launched in the market, forensic studies are being conducted to test data acquisition and analysis. However, since the application of new Android security technologies, it has become more difficult to acquire data using existing forensic methods. In order to address this problem, we propose a new acquisition method based on analyzing the firmware update protocols of Android smartphones. A physical acquisition of Android smartphones can be achieved using the flash memory read command by reverse engineering the firmware update protocol in the bootloader. Our experimental results demonstrate that the proposed method is superior to existing forensic methods in terms of the integrity guarantee, acquisition speed, and physical dump with screen-locked smartphones (USB debugging disabled).

High-Speed RSA crypto-processor with radix-4 modular multiplication and chinese remainder theorem

Today, RSA is one of the most popular public-key crypto-system in various applications. In this paper, we present a high-speed RSA crypto-processor with modified radix-4 Montgomery multiplication algorithm and Chinese Remainder Theorem (CRT). Our design takes 0.84M clock cycles for a 1024-bit modular exponentiation and 0.25M clock cycles for two 512-bit exponentiations. Using 0.18 um standard cell library, the processor achieves 365Kbps for a 1024-bit exponentiation and 1,233Kbps for two 512-bit exponentiations at a 300MHz clock rate. For the high performance RSA crypto-system, the processor can also execute modular reduction, which is essential for calculating the Montgomery mapping constant and the modularly reduced ciphertext in CRT technique.