A method that comprises obtaining a currently received signature from a device; obtaining a candidate identifier associated with the device; consulting a database to obtain a set of previously received signatures associated with the candidate identifier; and validating the currently received signature based on a comparison of the currently received signature to the set of previously received signatures associated with the candidate identifier. Also, a method that comprises obtaining a currently received signature from a device; decrypting the currently received signature to obtain a candidate identifier; and a candidate scrambling code; consulting a database to obtain a set of previously received scrambling codes associated with the candidate identifier; and validating the currently received signature based on a comparison of the candidate scrambling code to the set of previously received scrambling codes associated with the candidate identifier.
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