I have a sequence of bytes: https://drive.google.com/file/d/17sfchPgsySi2ilIxLuBb1q-UUqq5lO87
What the data is, is unknown (see NOTE below).
I'm pretty sure this data is compressed in some way, due to the ent analysis results:
$ ent first-chunk Entropy = 7.997831 bits per byte. Optimum compression would reduce the size of this 949674 byte file by 0 percent. Chi square distribution for 949674 samples is 2962.74, and randomly would exceed this value less than 0.01 percent of the times. Arithmetic mean value of data bytes is 127.3922 (127.5 = random). Monte Carlo value for Pi is 3.157487727 (error 0.51 percent). Serial correlation coefficient is 0.001738 (totally uncorrelated = 0.0).
According to the Chi square distribution the data is definitely not random. And compression is at an optimum. This leads me to believe the data is compressed and not encrypted. Is this a correct inference?
I've tried to decompress this data assuming the compression method to be zip, gz, xz, lz4, deflate, lzma, bzip, using tools like unlzma, gunzip, unzip, unlz4, zlib-flate etc. and none of them have worked. I always end up with a "file format not recognized" or a "invalid header check" error.
How do I find what compression method was used on the data? Could it be that the compression headers are missing?
This data is part of a slightly larger data file that is (possibly) the firmware and additional memory of a bluetooth speaker Flash memory. The whole file is: https://drive.google.com/file/d/1e9yG8xMkZ331C2TOTOzo9Y93L4abxX9F