The SHA-256 (Secure Hash Algorithm 256-bit) is a widely used cryptographic hash function that belongs to the SHA-2 (Secure Hash Algorithm 2) family. It is commonly employed in various security applications, including digital signatures, password hashing, and data integrity verification. SHA-256 generates a fixed-size 256-bit (32-byte) hash value from an input of arbitrary length.

Here’s a high-level overview of how the SHA-256 algorithm works:

1. Preprocessing: The input message is padded to meet specific requirements. It includes appending a 1-bit followed by zeros and adding a representation of the original message length to ensure a multiple of 512 bits.
2. Initialization: The algorithm starts with an initial set of constant values, called “constants” or “initial hash values,” represented as 32-bit words. These constants are derived from the fractional parts of the square roots of the first eight prime numbers.
3. Message Digest: The padded message is divided into blocks of 512 bits each. The algorithm processes each block in sequence.
4. Message Schedule: For each block, the 512 bits are divided into 16 words of 32 bits each.
5. Compression Function: The compression function operates on a set of eight working variables, represented as 32-bit words, which are initialized with the initial hash values. It applies multiple rounds of mixing, permutation, and bitwise operations to transform the data.
6. Hash Value: After processing all the blocks, the final values of the working variables represent the resulting hash value. The 256-bit hash is typically represented as a sequence of 64 hexadecimal characters.

The strength of SHA-256 lies in its properties, such as producing a fixed-size output, being resistant to collisions (finding two inputs with the same hash), and being computationally infeasible to reverse-engineer the original message from the hash value.

It’s important to note that while SHA-256 is widely used and considered secure for many purposes, cryptographic algorithms can evolve over time. It’s always recommended to stay informed about the latest advancements and best practices in the field of cryptography.