A Precise Decompression Method for Intel FPGA Bitstream

FPAG bitstream is a binary file containing chip configuration information. It is often compressed to conserve storage space and reduce configuration time. In this paper, we propose a precise decompression method for commercial FPGA bitstreams, which is a crucial step for assessing the security of FPGAs. In detail, by comparing the structure of compressed and uncompressed bitstream files, we identify the compression region, extract the compressed data, and construct a database with the mapping information. Then, we introduce a decoding algorithm that utilizes a sliding window approach in terms of the characteristics of the compression data. Finally, our decompression framework is validated on 24 different types of Intel FPGAs from 6 families, with a perfect accuracy rate of 100%.