Secret Key Generation from Channel Noise with the Help of a Common Key
This addresses secure communication for scenarios where channel characteristics are insufficient, offering a method to leverage noise and common keys, though it appears incremental as it builds on existing key generation and error-correcting techniques.
The paper tackles the problem of generating secret keys from channel noise when the channel lacks intrinsic advantages for legitimate receivers, using a pre-shared common key and error-correcting code to restrict information leaks to parity-check symbols. It quantifies security by the computational effort needed for exhaustive search, showing that noise enhances security by increasing common key candidates.
Information-theoretically secure communications are possible when channel noise is usable and when the channel has an intrinsic characteristic that a legitimate receiver (Bob) can use the noise more advantageously than an eavesdropper (Eve). This report deals with the case in which the channel does not have such an intrinsic characteristic. Here, we use a pre-shared common key as a tool that extrinsically makes Bob more advantageous than Eve. This method uses error-correcting code in addition to the common key and noise, and manages the three components in random-number transmission. Secret keys are generated from noise, and messages are encrypted with the secret keys in a one-time pad manner. As a result, information leaks meaningful to Eve are restricted to the parity-check symbols for the random numbers. It is possible to derive the candidates of the common key from the parity check symbols, and the security of this method is quantified in terms of the amount of computations needed for an exhaustive search of the candidates, where we evaluate the security by assuming that all parity check symbols leak to Eve without bit errors. Noise contributes to not only generating secret keys but also enhancing the security because the candidates of the common key increase with it.