Cryptography – Cryptanalysis
Patent
1984-01-12
1988-09-13
Cangialosi, Salvatore
Cryptography
Cryptanalysis
380 9, 380 48, H04R 110
Patent
active
047714557
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a scrambling apparatus which scrambles an audio signal by using a code and particularly to improve a scrambling apparatus for transmitting a signal series in which an audio signal is scrambled as an ordinary audio signal (of course the signal different from the scrambled audio signal).
BACKGROUND ART
A prior art scrambling apparatus is roughly classified into two types. In one type, the re-arrangement (scrambling) is carried out on a timebase, while in the other type, the re-arrangement is carried out on a frequency axis. In the scrambling apparatus for carrying out the rearrangement on the frequency axis, the signal series is divided into, for example, a plurality of frequency slots and the different frequency conversion is carried out at every slot. Upon re-arranging (descrambling), a frequency conversion reverse to the above frequency conversion is carried out to obtain the signal of the original frequency slot and thus the original signal series is obtained.
In the scrambling apparatus for performing the re-arrangement on the timebase, the signal series is divided into, for example, a plurality of frames. Then, these frames are re-arranged or a plurality of sampling data within the frame is re-arranged within a range of the frame. In the first example where the scrambling is performed on the timebase, the arranging and the rearranging on the timebase are performed as shown in FIG. 1.
In FIG. 1, reference numeral 1 designates a scrambling signal input terminal to which a signal to be scrambled (a scrambling signal) is inputted. The scrambling signal applied to this input terminal 1 is supplied through a trap circuit 2 and a low pass filter 3 to a PCM (pulse code modulation) encoder 4. The scrambling signal is pulse code-modulated by this PCM encoder 4, digitized and then fed to a scrambling circuit 5 in which the arranging on the timebase is performed. The data series thus scrambled is supplied to a composing circuit 6 in which it is added with a synchronizing signal which is supplied through a synchronizing signal input terminal 7. The synchronizing signal has the frequency of, for example, 2 KHz and is coincident with the characteristic of the afore-mentioned trap circuit 2. Namely, the scrambled signal is previously suppressed at its portion corresponding to the synchronizing signal. The data series passed through the composing circuit 6 is converted to an analog signal by a PCM decoder 8 and then supplied through a low pass filter 9 to a transmission path. This transmission path may be of either a wireless type construction or a wire type construction.
The low pass filters 3 and 9 are used to eliminate a noise and low pass filters 10 and 11, which will be mentioned later, are also used similarly. In the receiving system, the signal transmitted through the transmission path is delivered through the low pass filter 10 to a trap circuit 12 and a band pass filter 13. From this band pass filter 13 is derived the synchronizing signal of 2 KHz and this synchronizing signal is supplied to an automatic volume control circuit 14. The control signal therefrom is supplied to a PCM encoder 15 and in addition, the synchronizing signal itself is supplied to the PCM encoder 15. On the other hand, the signal series passed through the trap circuit 12 is PCM-modulated by the PCM encoder 15, which then is re-arranged on the timebase by a descrambling circuit 16. The data series thus re-arranged is converted to an analog signal by a PCM decoder 17 and delivered through the low pass filter 11 from an output terminal 18 to the outside.
By the way, in the above scrambling system, including the example shown in FIG. 1, the signal series to be transmitted can not just hide its appearance of the scrambled signal thoroughly regardless of the strength and weakness of the scrambling property, thereby urging a receiving person to decipher the code of the scrambled signal. As a result, the scrambling system which employs the simple code can be deciphered without difficulty. Acco
REFERENCES:
patent: 2129860 (1938-09-01), Mitchell
patent: 3406344 (1968-10-01), Hopper
patent: 3714622 (1973-01-01), Wilhelmsen
patent: 3921151 (1975-11-01), Guanella
patent: 4336554 (1982-06-01), Okada et al.
patent: 4340906 (1982-07-01), den Toonder et al.
patent: 4392021 (1983-07-01), Slate
patent: 4434323 (1984-02-01), Levine et al.
Hareyama Nobuo
Ohsawa Mitsuo
Cangialosi Salvatore
Sony Corporation
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