Irreversible Cryptographic Algorithms

B.

Out of the given options, the only cryptographic algorithm that is irreversible is SHA-256, so the correct answer is B.

Cryptographic algorithms are mathematical functions used for encrypting and decrypting data. They play a critical role in securing data transmissions and ensuring data confidentiality, integrity, and authenticity. Cryptographic algorithms can be classified into two categories: symmetric and asymmetric.

Symmetric algorithms use the same key for encryption and decryption, while asymmetric algorithms use different keys for encryption and decryption. Irreversible algorithms are also known as hash functions. They generate a fixed-length output, known as a hash, from an input data of any size. The hash function is designed to be one-way, meaning that it is impossible to reconstruct the original data from the hash.

Now let's take a look at each option and see why they are or aren't irreversible:

A. RC4: RC4 is a symmetric encryption algorithm, which means that it uses the same key for encryption and decryption. It is not irreversible.

B. SHA-256: SHA-256 is a hash function that generates a 256-bit hash from any input data. It is irreversible and is commonly used to ensure data integrity, digital signatures, and password storage.

C. DES: DES is a symmetric encryption algorithm that uses a 56-bit key. It is not irreversible.

D. AES: AES is a symmetric encryption algorithm that uses a variable key length of 128, 192, or 256 bits. It is not irreversible.

In conclusion, the only irreversible cryptographic algorithm among the given options is SHA-256, so the correct answer is B.