Method and adapter apparatus for securing information exchanged between a calling party and a called party. A first signal is generated, which is representative of an analog probe signal. The first signal is released towards the called party. Responsive to receipt from the called party of a second signal responsive to the analog probe signal and indicative of an ability of the called party to participate in a secure information exchange, negotiations are performed with the called party to securely exchange subsequent information with the called party. In this way, the adapter apparatus can securely exchange information without prior knowledge of whether the called party is secure-capable or secure-incapable and without prior knowledge of whether the called party is a POTS phone or a packet-switched device.