While there are several established protocols for end-to-end encryption, relatively little attention has been given to securely distributing the end-user public keys for such encryption. As a result, these protocols are often still vulnerable to eavesdropping by active attackers. Key Transparency is a protocol for distributing sensitive cryptographic information, such as public keys, in a way that reliably either prevents interference or detects that it occurred in a timely manner. In addition to distributing public keys, it can also be applied to ensure that a group of users agree on a shared value or to keep tamper-evident logs of security-critical events.