:::warning The Zorro Protocol is still under initial development. This draft reflects current thinking and will be updated without versioning as the protocol is implemented. ::: Introduction to Proof of Personhood Sybil attacks Many services and protocols suffer from attackers generating many accounts and using them to manipulate votes, extract resources, promulgate disinformation, etc. These are are known as sybil attacks. To secure themselves against sybil attacks, services would like to have evidence that each of their accounts is backed by a unique person acting under their own volition, i.e., to have some kind of proof of personhood for each account.