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SHA-256: The Cryptographic Hash Algorithm Explained

SHA-256, or Secure Hash Algorithm 256-bit, is a type of cryptographic hash function that is commonly used in various forms of digital security. A hash function is a mathematical algorithm that takes an input (or "message") and produces a fixed-size output, called a "hash" or "message digest," that is unique to the original input.

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SHA-256 is a specific type of hash function that produces a 256-bit hash value. The output of the SHA-256 algorithm is a fixed-size 256-bit (32-byte) hash.

SHA-256 is one of the most widely used cryptographic hash functions, and it is a part of the SHA-2 family of hash functions. It is considered to be a secure and robust algorithm, and it is used in a wide range of security applications such as digital signatures, password hashing, and data encryption.

Working of SHA-256

The working of the SHA-256 algorithm can be broken down into several steps:

  • Padding: The input message is padded with additional bits to ensure that its length is a multiple of 512 bits. This is done by appending a 1-bit followed by as many 0-bits as necessary to achieve the correct length.

  • Message Schedule: The padded message is then divided into blocks of 512 bits. These blocks are then processed by the algorithm to produce the message schedule, which is an array of 64 32-bit words.

  • Initialization: The algorithm starts with eight initial working variables, or "hashes," that are initialized to specific values. These values are known as the "initial hash values" and are based on the first 32 bits of the fractional parts of the cube roots of the first eight prime numbers.

  • Compression: The message schedule and the working variables are then processed through a series of logical operations, such as bitwise operations and modular additions, to produce a new set of working variables. This process is known as "compression" and is repeated for each block of the message.

  • Finalization: After all of the blocks have been processed, the final set of working variables is used to produce the final 256-bit hash value. This value is a unique representation of the original input message and is often referred to as the "message digest."

In summary, the SHA-256 algorithm takes an input message, pads it, divides it into blocks, processes the blocks using a series of logical operations and initial hash values, and finally produces a unique 256-bit hash value as the output, which represents the original input message.

Applications of SHA-256

SHA-256 is a widely used cryptographic hash function with various applications in the field of digital security. Some of the common applications of SHA-256 include:

  • Digital Signatures: SHA-256 is often used to generate a digital signature for a message or document. This ensures the authenticity of the message and verifies that it has not been tampered with.

  • Password Hashing: SHA-256 is used to hash passwords before they are stored in a database. This way, even if a hacker gains access to the database, they will not be able to determine the original passwords from the hashed values.

  • Data Encryption: SHA-256 is used to generate a unique encryption key that can be used to encrypt and decrypt data. This ensures that the data is unreadable without the proper encryption key.

  • Blockchain: SHA-256 is used in many blockchain platforms, including Bitcoin, to secure transactions on the blockchain.

  • File Integrity Verification: SHA-256 can be used to check the integrity of a file, by comparing the hash of the original file to the hash of the file after it has been transferred or stored.

  • SSL/TLS certificates: SHA-256 is used as a hashing algorithm to sign SSL/TLS certificates.

  • Network Security: SHA-256 is used in various network protocols for authentication and integrity of data.

  • File Authentication: SHA-256 is used in file authentication systems, to ensure the authenticity of files and check for tampering.

In short, SHA-256 is a widely used and widely accepted cryptographic hash function that is used in a variety of digital security applications, including digital signatures, password hashing, data encryption, blockchain, file integrity verification, network security and file authentication.

Pros and Cons of SHA-256

SHA-256 is a widely used and widely accepted cryptographic hash function, but like any technology, it has its own set of pros and cons.


  • Collision resistance: SHA-256 is considered to be collision-resistant, meaning that it is highly unlikely for two different inputs to produce the same hash value.

  • Widely used: SHA-256 is a widely used cryptographic algorithm and is accepted by many industries and organizations.

  • Secure: SHA-256 is considered to be a secure algorithm and is used in various forms of digital security.

  • Fast: SHA-256 is a fast algorithm and can quickly process large amounts of data.

  • Long Hash: SHA-256 produces a long hash of 256-bit, making it more difficult for an attacker to find collisions


  • Not quantum-computer resistant: SHA-256 is vulnerable to attacks by quantum computers, which can potentially break the encryption and compromise the security of the data.

  • Not suitable for small inputs: SHA-256 is not suitable for small inputs, as the hash value produced is always the same size, regardless of the size of the input.

  • Not suitable for Real-time Applications: SHA-256 can be slow for real-time applications, as the hash function takes a certain amount of time to process the input.

  • Not completely future-proof: As computational power increases over time, it's possible that SHA-256 will become less secure in the future, and new hash functions will need to be developed to replace it.

In conclusion, SHA-256 is a robust and widely used cryptographic hash function, but it is not completely future-proof and not suitable for real-time applications. It's important to evaluate the specific needs of your application and use the appropriate cryptographic method accordingly.

Bottom Line

Overall, SHA-256 is a powerful and widely used cryptographic hash algorithm that plays a critical role in keeping our digital information secure. It is a one-way process and collision resistance which makes it a secure algorithm for the digital security.

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