A method for securing communications in a vehicle-to-vehicle (V2V) system including an on-board computer of a broadcasting vehicle predicting a value for a vehicle parameter, generating a heavyweight signature corresponding to the predicted value, and obtaining an actual value for the vehicle parameter. The method also includes the computer comparing the predicted value to the actual value to determine if the predicted value bears a first relationship to the actual value. If the computer determines that the predicted value bears the relationship to the actual value, the on-board computer generates a lightweight authenticating signature to correspond to the predicted value and broadcasts a data message having the predicted value with the corresponding heavyweight authenticating signature and the corresponding lightweight authenticating signature.