Stream and Block Ciphers

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Block ciphers and stream ciphers are the two types of encryption ciphers.

Block Ciphers – They are encryption ciphers that operate by encrypting a fixed amount, or “block,” of data. The most common block size is 64 bits of data. This chunk or block of data is encrypted as one unit of cleartext. When a block cipher is used for encryption and decryption, the message is divided into blocks of bits. Blocks are then put through one or more of the following scrambling methods like substitution, transposition, confusion and diffusion.

Stream Cipher – It encrypts single bits of data as a continuous stream of data bits. Stream ciphers typically execute at a higher speed than block ciphers and are suited for hardware usage. The stream cipher then combines a plain text bit with a pseudorandom cipher bit stream by means of an XOR (exclusive OR) operation.

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