I have firmware for a system and I'm trying to decrypt some of it just for the sake of seeing what it all does; nothing illegal or anything like that, such as reproducing copies of it decrypted and such.
But it can seem tough for several reasons:
1.May have no specific format or way to distinguish it from other binary files;
2.May not know how it is encrypted;
3.May not be "normally" encrypted and may be specially so.
The thing is, the file has some unencrypted code, but I'm not 100% sure what kind of opcode bytes it could represent since it
This is firmware for an all-ARM-powered device, but I'm not publicly saying it's name. Should that mean that the firmware for it will be some variant of ARM ISA/opcodes (because it's machine code for the ARM processor)? If so, where should I begin decrypting and should I continue to determine, if possible for me, what version of ARM, ISA (instruction-set=architecture), etc.?
The firmware has a magic number right at the beginning of the file (which just says the company's name), but afterwards it has unencrypted bytes, then more magic numbers, then encrypted bytes, then more magic numbers, then more unencrypted bytes, etc., etc. You can tell the encrypted parts apart because each byte has a completely inane ASCII character that no other part of the file has, and they're in followed segments. This says clearly that these are irregular, encrypted ranges of bytes.