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Section 2.8 Stream Ciphers

Stream ciphers encode data one symbol at a time and produces one ciphertext symbol for each cleartext symbol. Given that you can often use some sort of block encryption with a significantly small block size, stream encryption is not used as often. Technically the OTP example, when used one symbol at a time, is a stream cipher. The keys come in one symbol at a time, the cleartext comes in one symbol at a time, and an operation is performed (addition in the case of the example) to create the ciphertext. Given a suitable keysize and a well-researched algorithm, stream ciphers can be just as secure as block ciphers. That being said a stream cipher is usually more consistent in its runtime characteristics and typically consumes less memory Unfortunately there are not as many well-researched algorithms and widely used stream ciphers.
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