Initialization vector (IV)

An initialization vector (IV) is a random number used in cryptography that is applied to the first block of text in a message before it is encrypted. The purpose of the IV is to ensure that identical messages have different ciphertexts.

IVs are typically generated randomly and kept secret. They must be the same size as the block size of the cipher, which is typically 16 bytes for AES. For example, if AES is being used with a 16-byte block size, the IV would also be 16 bytes.

In some modes of operation, such asCBC, the IV must be unique for each message encrypted with the same key. This is because if the same IV is used for two different messages, an attacker could potentially decrypt both messages.

Some modes of operation, such as CTR, do not require a unique IV for each message. In these modes, the IV can be public and does not need to be kept secret.

What is IV and key in AES?

In cryptography, an initialization vector (IV) is a fixed-size input to a cryptographic primitive that is typically required to be random or pseudorandom. IVs are commonly used in stream ciphers and block ciphers; the latter are more often referred to as nonces rather than IVs.

A key is a piece of information that controls the cryptographic process and permits an encrypted message to be decrypted. Keys are also used with digital signatures, for both message integrity and authentication.

What is IV in CBC?

In CBC (Cipher-Block-Chaining) mode, each block of plaintext is XORed with the previous ciphertext block before being encrypted. This way, each ciphertext block is "chained" to the previous one, and plaintext blocks that are close together will produce ciphertext blocks that are also close together.

The IV (Initialization Vector) is a block of random data that is used to "seed" the first block of plaintext. It ensures that even if the same plaintext is encrypted more than once, the resulting ciphertext will be different each time.

The IV does not need to be kept secret; in fact, it needs to be known by the sender and receiver of the ciphertext in order to decrypt it. However, it should never be reused with the same key, or the security of the cipher will be compromised. What is salt and IV in encryption? Salt and IV are two common concepts in encryption. Salt is a randomly generated number that is used as an additional input to a one-way function that "hashes" data. IV is a bit pattern that is used as an initialization vector to a block cipher.

Why IV should be random?

IVs should be random for two main reasons:

1. To ensure that each message encrypted with the same key has a unique ciphertext.

2. To prevent attackers from using known plaintext attacks.

If IVs were not random, then an attacker could simply encrypt the same message multiple times with the same key and compare the resulting ciphertexts. If they were identical, then the attacker would know that the same key was used to encrypt both messages. By using a different IV for each message, we can ensure that identical messages will always result in different ciphertexts.

Similarly, if an attacker has access to a large number of ciphertexts that were all encrypted with the same key, they could potentially use known plaintext attacks to recover the key. By using a different IV for each message, we can make it much more difficult for attackers to mount known plaintext attacks.

Why is IVs unique?

IVs are unique because they are randomly generated numbers that are used in conjunction with a user's password to encrypt data. This means that even if two users have the same password, their data will be encrypted differently because their IVs will be different.