Encryption/decryption system

An encryption/decryption system for encrypting an input digital signal at the transmitting end of a communications channel and for reproducing the input signal at the receiving end, said system comprising:

• at the transmitting end:
• encrypted signal composing means for combining a randomized coding signal with the input digital signal to form an encrypted signal segmented into frames;
• first register means having storing contents comprising a predetermined number of bits m of the encrypted signal output from the composing means and for outputting a plurality of the stored bits in parallel;
• first random number generator means for locally generating a first random number for each frame;
• first selecting means for randomly selecting based on said first random number an output, for each signal frame, responsive to the m bit number data output by the first register means and for outputting corresponding n bit address numbers, where n is an integer which is at least 2;
• and
• first memory means for producing the bits of the randomized coding signal responsive to receiving the n bit addresses output from the first selecting means by outputting for each address a corresponding random bit which is prestored at the address;
• and at the receiving end:
• second register means for storing m bits of a received encrypted signal and for outputting a plurality of the stored bits in parallel;
• second random number generator means for locally generating a second random number for each frame in sync with a corresponding frame of the encrypted signal;
• second selecting means, operating the same way as the first selecting means and in sync with said corresponding frame of the encrypted signal, for selecting based on a second random number an output responsive to the m bit number data output by the second register means and outputting corresponding n bit address numbers;
• second memory means, having stored contents which are identical to the contents stored in the first memory means, said second memory means producing a prestored decoding signal responsive to receiving the n bit addresses output from the second selecting means, said second memory means outputting a corresponding random bit prestored at the corresponding address;
• and
• digital signal reproducing means for combining the received encrypted signal with the decoding signal to reproduce the input digital signal.

An encryption/decryption system comprising:

• means for storing a plurality of identical encryption/decryption keys at opposite ends of a communication channel;
• means for identifying each of said keys by a first address to form first random data, said first address being derived from a randomized digital signal which is segmented into frames;
• first generator means for locally generating a first random number for each frame of said randomized digital signal;
• first selector means for randomly selecting based on said first random number an output from among said first random data in order to form second random data;
• means for combing an input digital signal with said second random data to produce said randomized digital signal;
• means responsive to the receipt of the randomized digital signal which is transmitted over said channel for identifying each of said keys by a second address in order to form third random data, said second address being derived from the received randomized digital signal;
• second generator means for locally generating a second random number corresponding to said first random number;
• second selector means for randomly selecting, based on said second random number an output from among said third random data in order to form fourth random data;
• and
• means for combining said received randomized digital signal with said fourth random data to reproduce the input digital signal.

An encryption/decryption system comprising:

• means for storing a plurality of identical encryption/decryption keys at opposite ends of a communication channel;
• first generator means for locally generating a first random number for each frame of a randomized digital signal which is segmented in frames;
• first selector means for randomly selecting based on said first random number an output from among first data to form a first address, said first data being derived from a randomized digital signal;
• means for combining an input digital signal with said first random data to produce said randomized digital signal;
• second generator means for locally generating a second random number corresponding to said first random number;
• second selector means for randomly selecting, based on said second random number an output from among second data to form a second address, said second data being derived from the randomized digital signal which is transmitted over said channel;
• means for identifying each of said keys by said second address to form second random data;
• and
• means for combining the received randomized digital signal with said second random data to reproduce the input digital signal.