22 block cipher modes of operation part 1 cns

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okay, let's dive into the fascinating world of block cipher modes of operation! we'll cover a significant chunk of them (22, as requested) while focusing on the core concepts and practical implementations. due to the length, this is part 1.

**important preliminary notes**

* **block ciphers:** a block cipher (like aes, des, or blowfish) operates on fixed-size blocks of data (e.g., 128 bits for aes). modes of operation extend the use of a block cipher to encrypt data of arbitrary length.
* **key concepts:**
* **encryption:** the process of transforming plaintext (readable data) into ciphertext (unreadable data).
* **decryption:** the reverse process, transforming ciphertext back into plaintext.
* **initialization vector (iv):** a non-secret random value used to ensure that encrypting the same plaintext multiple times produces different ciphertexts. crucial for modes like cbc, cfb, ofb, and ctr. *must be unpredictable (ideally random) for security.*
* **padding:** since block ciphers operate on fixed-size blocks, padding schemes are often used to ensure the plaintext length is a multiple of the block size. common padding schemes include pkcs7/pkcs5.
* **nonce:** a "number used once." similar to an iv, but often used with authenticated encryption modes. sometimes predictable, but must be unique for each encryption operation using the same key.
* **authenticated encryption:** modes that provide both confidentiality (encryption) and integrity (authentication). they ensure the data hasn't been tampered with.
* **parallelizability:** the ability to perform encryption or decryption of different blocks concurrently.
* **error propagation:** the extent to which an error in one ciphertext block affects the decryption of subsequent blocks.
* **library:** we'll use `cryptography` library, which you can install using pip: `pip install cryptography`.

**part 1: the fundamental modes**

1. **electronic codebook ( ...

#BlockCipher #Cryptography #python
block cipher
modes of operation
encryption
decryption
cryptography
symmetric key
CBC mode
ECB mode
CFB mode
OFB mode
CTR mode
GCM mode
authentication
security
data integrity