Abstract: A security key holder system permits an access key to be released to an authorized individual at a remote location. The access key is secured by a decoder unit that is installed within a vehicle or at a fixed site. To access the key, a person places a call via telephone or radio to a dispatcher station, and applies an identification device to a touch receptacle of the decoder unit. Under the control of a dispatcher, an encoder unit generates an encrypted key release code using the state of an internal real time clock to select an encryption method. The encrypted code is transmitted over an RF radio channel, over the telephone system, or over a dedicated cable, depending upon the installation (mobile or base) of the target decoder unit. Decoder units that receive the transmission use their respective real time clocks to select a decryption method.