Which of the following are examples of block ciphers?

The identification of block ciphers within the context of encryption standards is significant for understanding how data is securely processed. Block ciphers are cryptographic algorithms that encrypt data in fixed-size blocks, making them suitable for various applications in data security.

3DES (Triple Data Encryption Standard) and AES (Advanced Encryption Standard) are both prominent examples of block ciphers. 3DES operates by applying the DES encryption algorithm three times to each data block, thereby enhancing its security compared to the original DES. AES, on the other hand, is a more modern and efficient block cipher that supports key sizes of 128, 192, and 256 bits, allowing for strong encryption across a variety of applications.

In contrast, RC4 is a stream cipher, which encrypts data in a continuous stream rather than in fixed blocks. Modes of operation, such as CBC (Cipher Block Chaining) or ECB (Electronic Codebook), define how block ciphers are used on varying amounts of data but are not themselves block ciphers. Likewise, hash algorithms, like SHA-256, are used for generating fixed-size hashes from input data and do not fall under the category of block ciphers as they serve different purposes in cryptography.

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