In exemplary embodiments of the present invention, a V2V unit in a vehicle (OBE) can, for example, store a plurality of years of encrypted certificates. The certificates can, for example, be programmed at an OBE factory using a secure server, and access to all certificates can be locked until an unlock key is computed for a given window (certificate validity period). An in-vehicle satellite receiver can then receive, over, for example, a dedicated satellite control channel, unlock codes for a current time window and a next time window, and provide them to the V2V device. Using those unlock codes, the V2V device (OBE) can compute an unlock key from an unlock code provided by the satellite receiver. In this manner an in-vehicle device may be directly messaged, but only to unlock one or more certificates at a controlled time. Without the received lock codes, the stored certificates are not useable.