A replaceable printer component includes a first memory device and a communication link. The first memory device is configured to store a first secret. The communication link is configured to communicatively link the first memory device to a printer controller when the replaceable printer component is installed in a printing system. The printing system comprises a second memory device storing a second secret. The second memory device is communicatively linked to the printer controller. The printer controller is configured to determine an authenticity of the replaceable printer component based on the first secret and the second secret.