Introduction to Cryptography
Block ciphers and stream ciphers are two types of symmetric-key encryption methods used in cryptography. While both are used to encrypt data, they operate differently and are best suited for different use cases.
Block ciphers encrypt plaintext in fixed-size blocks, typically 64 or 128 bits. The input block is processed through a series of mathematical operations called rounds, with each round transforming the input in a non-linear and reversible way. The output of each round is used as the input for the next round until the final output is produced. The encryption and decryption keys are used to define the specific transformation used in each round.
One of the most popular block ciphers is Advanced Encryption Standard (AES), which supports key sizes of 128, 192, or 256 bits. AES is widely used in applications that require a high level of security, such as financial transactions and government communications.
Stream ciphers, on the other hand, encrypt data one bit or byte at a time, usually by generating a pseudorandom stream of bits that is combined with the plaintext using a bitwise XOR operation. The same pseudorandom stream is used for both encryption and decryption, and the encryption and decryption keys are used to initialize the pseudorandom number generator.
Stream ciphers are often used in applications that require high performance and low latency, such as real-time communications and multimedia streaming. However, they are generally considered to be less secure than block ciphers because they are vulnerable to certain types of attacks, such as keystream reuse attacks.
In summary, block ciphers are best suited for applications that require a high level of security, while stream ciphers are best suited for applications that require high performance and low latency. Understanding the differences between these two types of ciphers is essential for making informed decisions about which encryption method to use for a particular application.
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