We present an anti-piracy locking-based design methodology for RF transceivers, called SyncLock. SyncLock acts on the synchronization of the transmitter with the receiver. If a key other than the secret one is applied the synchronization and, thereby, the communication fails. SyncLock is implemented using a novel locking concept. A hard-coded error is hidden into the design while the unlocking, i.e., the error correction, takes place at another part of the design upon application of the secret key. SyncLock presents several advantages. It is generally applicable, incorrect keys result in denial-of-service, it incurs no performance penalty and minimum overheads, and it offers maximum security thwarting all known counterattacks. We demonstrate SyncLock with hardware measurements.