title: is it possible reverse SHA1 hash to binary?
body: <p>Given the byte size and SHA1 hash (20 bytes),
  can binary data be generated to fit a given SHA1 hash?
  For example, given a hash of 16KB size and A, a meaningless binary file with an A hash value is created.
  Is it possible? If possible, in what direction can I write the code?</p>