A computer-implemented method comprising: with a first unit, (a) receiving an encryption key from a remotely located key provisioning unit, wherein the remotely located key provisioning unit includes a server wirelessly coupled to the first unit and a second unit; (b) sensing first local environmental sensory data and determining a first feature based on the first sensed local environmental sensory data, the first feature being a mel-frequency cepstrum, MFC; (c) encrypting the first feature based on the encryption key and indiscriminately broadcasting the encrypted first feature directly to the second unit; (d) receiving an encrypted second feature directly from the second unit, the second unit being separate from but locally nearby the first unit and the second feature being based on the first local environmental sensory data; decrypting the received encrypted second feature using a key that is related to the received encryption key; correlating the decrypted second feature received from the second unit with the first feature; and (e) based on the first and second features, discriminately communicating additional data directly between the first and second units; wherein the first unit includes a first identifier, ID to identify the first unit and the second unit includes a second ID to identify the second unit; the method further including, based on the comparison of the first and second features, the first unit wrapping a session key with the encryption key, transmitting that session key to the second unit and establishing a secure channel between the first and second unit based on the session key. with a first unit, (a) receiving an encryption key from a remotely located key provisioning unit, wherein the remotely located key provisioning unit includes a server wirelessly coupled to the first unit and a second unit; (b) sensing first local environmental sensory data and determining a first feature based on the first sensed local environmental sensory data, the first feature being a mel-frequency cepstrum, MFC; (c) encrypting the first feature based on the encryption key and indiscriminately broadcasting the encrypted first feature directly to the second unit; (d) receiving an encrypted second feature directly from the second unit, the second unit being separate from but locally nearby the first unit and the second feature being based on the first local environmental sensory data; decrypting the received encrypted second feature using a key that is related to the received encryption key; correlating the decrypted second feature received from the second unit with the first feature; and (e) based on the first and second features, discriminately communicating additional data directly between the first and second units; wherein the first unit includes a first identifier, ID to identify the first unit and the second unit includes a second ID to identify the second unit; the method further including, based on the comparison of the first and second features, the first unit wrapping a session key with the encryption key, transmitting that session key to the second unit and establishing a secure channel between the first and second unit based on the session key.