Electronic Code Book

Electronic Code Book (ECB) is a basic mode of operation in which the encrypted data is produced as a result of applying the encryption algorithm one-by-one to each block of plaintext. This is the most straightforward mode, but it should not be used in practice as it is insecure and can reveal information:

The preceding diagram shows that we have plaintext P provided as an input to the block cipher encryption function, along with a key KEY and ciphertext C is produced as output.