Initialization vector: Difference between revisions

Revision as of 11:34, 12 March 2024

Revision as of 08:47, 29 April 2024

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==Motivation==

[[File:Tux ecbECB.jpgpng|thumb|Insecure encryption of an image as a result of [[electronic codebook]] mode encoding.]]

A [[block cipher]] is one of the most basic [[cryptographic primitive|primitive]]s in cryptography, and frequently used for data [[encryption]]. However, by itself, it can only be used to encode a data block of a predefined size, called the [[block size (cryptography)|block size]]. For example, a single invocation of the [[Advanced Encryption Standard|AES]] algorithm transforms a 128-bit [[plaintext]] block into a [[ciphertext]] block of 128 bits in size. The [[cryptographic key|key]], which is given as one input to the cipher, defines the mapping between plaintext and ciphertext. If data of arbitrary length is to be encrypted, a simple strategy is to split the data into blocks each matching the cipher's block size, and encrypt each block separately using the same key. This method is not secure as equal plaintext blocks get transformed into equal ciphertexts, and a third party observing the encrypted data may easily determine its content even when not knowing the encryption key.