Definition
A block cipher mode of operation for safely applying a cryptographic algorithm that works on fixed-length blocks to long plaintext data
Visual IT Encyclopedia › Information Security › Cryptography
Visual IT Encyclopedia › Information Security › Cryptography
Definition
A block cipher mode of operation for safely applying a cryptographic algorithm that works on fixed-length blocks to long plaintext data
Setup: Blocks are shortened to 16 bits (4 hex digits); AES uses 128 bits. E is an encryption function that turns one block into a different value with key K. The same input always gives the same output. Only the encryption direction is drawn.
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Electronic Codebook (ECB)
A block cipher can encrypt only one block of a fixed size at a time. A long message therefore has to be split into blocks, and a block cipher mode of operation defines how those blocks are chained together when encrypting. Each scheme, such as ECB or CBC, is also called a mode. ECB feeds each block into E as it is and encrypts it separately.
Example: Alice encrypts a three-block message and sends it. Plaintext blocks 1 and 3 have the same value (3A7C). Can Eve, who sees only the ciphertext, tell that?