Proof of work required. Your browser will mine a partial SHA-256
collision before the message can be submitted. This takes approximately
90 seconds. Think of it as a CAPTCHA for people who appreciate
cryptographic hash functions.
Protocol: Hashcash-style proof of work (SHA-256)
Difficulty:-- leading zero bits
Estimated time: ~90 seconds
Algorithm: Find counter where SHA-256(nonce + ":" + counter)
has the required leading zero bits