This challenge is *not* trivially brute-forceable.

Each connection requires both creating a SHA with 7 leading zeroes given some input,
*as well as* solving a non-automatable captcha.

You receive the hash input on one connection, and are given 5 minutes to 
reconnect with the solution.

Example:
  Challenge: 
    Gsm4KuopyQmX/O6eJGjXGu85E2b+GhkKqPaaIzwfxFI=
  Generated input, challenge appended:
    OP2zpH4p24/DW7k+bIxoyDsBVUDEuFvuK1s9alnp/N0aybgq6inJCZf87p4kaNca7zkTZv4aGQqo9pojPB/EUg==
  Hash of generated input:
    0000000b56082626211f9ef035f57157af21cdc4
  Correct response:
    OP2zpH4p24/DW7k+bIxoyDsBVUDEuFvuK1s9alnp/N0=

On the second connection, you are given the captcha image and ~20 seconds
to respond with the captcha solution and the SHA response.  Each new
connection pair gives a new SHA challenge and captcha to solve.

I've included some sample images of captchas in case people want to try
automating them.

There is a solution which does not require any brute-forcing.