Cryptography – Cryptanalysis
Patent
1985-12-23
1987-11-10
Cangialosi, Salvatore
Cryptography
Cryptanalysis
380 49, 380 59, 360 53, H04L 900
Patent
active
047062827
ABSTRACT:
An improved decoder for a recorder-decoder system wherein a threshold level detector is included in the decoder. The recorder provides for the recording of an audio signal plus a data signal. The data signal includes zero crossing information for sequential increments of time plus an indication of whether the threshold level was met for an increment of the recorded audio. Upon playback the decoder also provides a data signal based on the recorded audio. The threshold level detector of the decoder is higher than that of the recorder. If the recorded data signal indicates the threshold was not met and the same threshold indication is not provided by the threshold level detector of the decorder for the corresponding increment of the recorded audio signal, tampering of such audio increment of the recorded audio is considered to have occurred.
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Cangialosi Salvatore
Lewis Aaron J.
Marben Robert L.
Minnesota Mining and Manufacturing Company
Sell Donald M.
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