Krypteringsmoduserna

Krypteringsmoduserna, also known as encryption modes, are specific procedures or algorithms that dictate how a block cipher is applied to encrypt data. A block cipher encrypts data in fixed-size blocks, but most data is larger than these blocks. Encryption modes specify how to handle multiple blocks and maintain security across them. Without proper modes, even a strong block cipher could be vulnerable to certain attacks, such as repeating patterns in the plaintext becoming visible in the ciphertext.

Several modes exist, each with different properties and use cases. Electronic Codebook (ECB) is the simplest mode, encrypting each block independently. While easy to implement, it is generally not recommended for most applications due to its weakness against pattern analysis. Cipher Block Chaining (CBC) links each ciphertext block to the previous one through an XOR operation, making the encryption of each block dependent on all preceding blocks and thus more secure than ECB.

Cipher Feedback (CFB) and Output Feedback (OFB) modes turn a block cipher into a stream cipher. CFB encrypts a block and then uses part of the ciphertext to generate the keystream for the next block. OFB generates a keystream independently of the plaintext and ciphertext, making it less susceptible to transmission errors. Counter (CTR) mode is another stream cipher mode that generates a keystream by encrypting successive values of a counter. It allows for parallel processing of encryption and decryption, offering performance advantages. The choice of encryption mode is crucial for the overall security of a cryptographic system and depends on factors like the type of data being encrypted, performance requirements, and desired security properties.