Stream ciphers typically process information byte by byte or bit by bit. Generally speaking
- The key length of the stream cipher will be the same as the length of the plaintext.
- The key of the stream cipher is derived from a shorter key, and the derived algorithm is usually a pseudo-random number generation algorithm.
It should be noted that stream encryption is currently symmetric encryption.
The more random the sequence generated by the pseudo-random number generation algorithm, the better the statistical features in the plaintext are covered.
Stream cipher encryption and decryption is very simple, and in the case of known plaintext, the key stream can be obtained very easily.
The key to stream ciphers is the well-designed pseudo-random number generator. In general, the basic building block of a pseudo-random number generator is a feedback shift register. Of course, there are also some specially designed stream ciphers, such as RC4.
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