The Topos Reliable Broadcast protocol of the TCE tolerates up to a fraction f of Byzantine processes in order to ensure its properties of validity and agreement. Such requirement is simple to achieve in a permissioned setting as malicious participants can be excluded from the system, but this is a notoriously hard task in open systems with free membership like the TCE. Like any permissionless system, the TCE is vulnerable to adversarial behaviors consisting in creating fake identities, i.e., Sybil attacks.