Blokcijfers

Blokcijfers, also known as block ciphers, are a fundamental type of symmetric encryption algorithm. They operate on fixed-size blocks of plaintext data, encrypting each block independently to produce a corresponding block of ciphertext. The size of these blocks is a defining characteristic of a block cipher, typically ranging from 64 bits to 128 bits or more. A key is used to control the encryption and decryption process. The same key is used for both operations, which is characteristic of symmetric encryption.

The process of block cipher encryption involves a series of substitutions and permutations applied in rounds. These operations are designed to be reversible, allowing the original plaintext to be recovered from the ciphertext using the same key. Common examples of block ciphers include the Data Encryption Standard (DES), Triple DES (3DES), and the Advanced Encryption Standard (AES). AES, in particular, is widely used today due to its strong security and efficiency.

Block ciphers are often used in conjunction with modes of operation, such as Electronic Codebook (ECB), Cipher Block Chaining (CBC), and Counter (CTR) mode. These modes dictate how multiple blocks of data are encrypted, influencing the security and properties of the overall encryption scheme. For instance, CBC mode links consecutive blocks, making the ciphertext dependent on all preceding plaintext blocks, which enhances security compared to ECB mode's independent block encryption.