Simple number verification/second factor authentication service.

Send an SMS with the PIN, and get a hash to verification:

Request: POST /?number=13215551212 Response: {"hash":"0021e28230ff8ba40165e595ef7cbe21214b34d6"}

Verify the correct PIN:

Request: GET /?hash=0021e28230ff8ba40165e595ef7cbe21214b34d6&number=13215551212&pin=7901 Response: {"valid":true}

Verify an incorrect PIN:

Request: GET /?hash=0021e28230ff8ba40165e595ef7cbe21214b34d6&number=13215551212&pin=7900 Response: {"valid":false}