| 摘要 |
For speech encryption, clear signals (K1) in the form of speech segments of equal duration are permuted in a transmitter-side code modulator (SM), using code signals (S1) from a code generator (SG1). In a receiver-side demodulator (RM), the speech segments of the encrypted signal (VS) are permuted back into the clear signal (K2), using code signals (S2) from another code generator (SG2). To make unauthorised and systematic demodulation difficult, speech segments which are successive in the clear signal (K1) are not allowed to be successive in the encrypted signal (VS). At the same time, encryption is carried out so that all permutations appear equally often in the encrypted signal (VS). This makes the work of decryption for an unauthorised third party all the more difficult. This method is broken into steps so that it can be implemented with simple digital components. <IMAGE> |
