What is an initialization vector in encryption?

A. I. A continuously changing number used in combination with a secret key to encrypt data. Initialization vectors (IVs) are used to prevent a sequence of text that is identical to a previous sequence from producing the same exact ciphertext when encrypted.

How does CBC encryption work?

In CBC mode, the current plaintext block is added to the previous ciphertext block, and then the result is encrypted with the key. Decryption is thus the reverse process, which involves decrypting the current ciphertext and then adding the previous ciphertext block to the result.

What is CBC mode in cryptography?

Cipher block chaining (CBC) is a mode of operation for a block cipher — one in which a sequence of bits are encrypted as a single unit, or block, with a cipher key applied to the entire block. It is used in this case to facilitate the combination of plaintext blocks and encryption keys.

Should initialization vector be encrypted?

In cipher-block chaining mode (CBC mode), the IV need not be secret, but must be unpredictable (In particular, for any given plaintext, it must not be possible to predict the IV that will be associated to the plaintext in advance of the generation of the IV.) at encryption time.

What is the use of initialization vector in AES?

An initialization vector (or IV) are used to ensure that the same value encrypted multiple times, even with the same secret key, will not always result in the same encrypted value. This is an added security layer.

Why do we need initialization vector?

An initialization vector is used to avoid repetition during the data encryption process, making it impossible for hackers who use dictionary attack to decrypt the exchanged encrypted message by discovering a pattern.

Is CBC mode secure?

The block cipher modes ECB, CBC, OFB, CFB, CTR, and XTS provide confidentiality, but they do not protect against accidental modification or malicious tampering. Modification or tampering can be detected with a separate message authentication code such as CBC-MAC, or a digital signature.

What is the difference between ECB and CBC encryption?

ECB (Electronic Codebook) – is essentially the first generation of the AES. It is the most basic form of block cipher encryption. CBC (Cipher Blocker Chaining) – is an advanced form of block cipher encryption. This adds an extra level of complexity to the encrypted data.

What is CBC mode in AES?

CBC (short for cipher-block chaining) is a AES block cipher mode that trumps the ECB mode in hiding away patterns in the plaintext. CBC mode achieves this by XOR-ing the first plaintext block (B1) with an initialization vector before encrypting it. The same initialization vector (C0) will be used for decryption.

What properties should initialization vector have?

An IV is prepended to a plaintext message in order to strengthen the encryption. The IV is truely random. Each message has its own unique IV. Timestamps and cryptographic hashes are sometimes used instead of random values, but these are considered to be insecure as timestamps can be predicted.

Do we need to encrypt IV?

In any case, the IV never needs to be kept secret — if it did, it would be a key, not an IV. Indeed, in most cases, keeping the IV secret would not be practical even if you wanted to since the recipient needs to know it in order to decrypt the data (or verify the hash, etc.).

What is the use of initial vector in CBC?

In Cipher Block Chaining (CBC) mode, an initialization vector (IV) is added to the first block of plaintext before encryption and the resultant ciphertext is added to the next block of plaintext before encryption, and so on. Decryption is the reverse process.

How is an initialization vector added in CBC?

How is CBC mode used in a block cipher?

CBC mode is a commonly used mode of operation for a block cipher. It works by XOR-ing an IV with the initial block of a plaintext prior to encryption and then XOR-ing each successive block of plaintext with the previous block of ciphertext before encryption. When used properly, CBC mode provides security against chosen plaintext attacks.

How is the IV used in CBC mode?

As you see in the decryption schema, the IV is used for a single XOR that yields the first plaintext block; it is obvious that the IV impacts only that block. When encrypting, though, modifying the IV alters the first ciphertext block, then the second ciphertext block, and so on.

How is CBC mode used in ECB mode?

CBC mode eliminates a weakness of Electronic Code Book (ECB) mode by allowing identical plaintext blocks to be encrypted to different ciphertext blocks. This is possible by the XOR-ing of an IV with the initial plaintext block so that every plaintext block in the chain is XOR’d with a different value before encryption.