Among the many advancements seen in network security, encryption and hashing have been the core principles of additional security modules. The secure hash algorithm with a digest size of 256 bits, or the SHA 256 algorithm, is one of the most widely used hash algorithms. While there are other variants, SHA 256 has been at the forefront of real-world applications.

To understand the working of the SHA 256 algorithm, you need first to understand hashing and its functional characteristics.

## What is Hashing?

Hashing is the process of scrambling raw information to the extent that it cannot reproduce it back to its original form. It takes a piece of information and passes it through a function that performs mathematical operations on the plaintext. This function is called the hash function, and the output is called the hash value/digest.

As seen from the above image, the hash function is responsible for converting the plaintext to its respective hash digest. They are designed to be irreversible, which means your digest should not provide you with the original plaintext by any means necessary. Hash functions also provide the same output value if the input remains unchanged, irrespective of the number of iterations.

There are two primary applications of hashing:

- Password Hashes: In most website servers, it converts user passwords into a hash value before being stored on the server. It compares the hash value re-calculated during login to the one stored in the database for validation.

- Integrity Verification: When it uploads a file to a website, it also shared its hash as a bundle. When a user downloads it, it can recalculate the hash and compare it to establish data integrity.

Now that you understand the working of hash functions, look at the key topic in hand - SHA 256 algorithm.

## What is the SHA-256 Algorithm?

SHA 256 is a part of the SHA 2 family of algorithms, where SHA stands for Secure Hash Algorithm. Published in 2001, it was a joint effort between the NSA and NIST to introduce a successor to the SHA 1 family, which was slowly losing strength against brute force attacks.

The significance of the 256 in the name stands for the final hash digest value, i.e. irrespective of the size of plaintext/cleartext, the hash value will always be 256 bits.

The other algorithms in the SHA family are more or less similar to SHA 256. Now, look into knowing a little more about their guidelines.

## What are the Characteristics of the SHA-256 Algorithm?

Some of the standout features of the SHA algorithm are as follows:

- Message Length: The length of the cleartext should be less than 264 bits. The size needs to be in the comparison area to keep the digest as random as possible.
- Digest Length: The length of the hash digest should be 256 bits in SHA 256 algorithm, 512 bits in SHA-512, and so on. Bigger digests usually suggest significantly more calculations at the cost of speed and space.
- Irreversible: By design, all hash functions such as the SHA 256 are irreversible. You should neither get a plaintext when you have the digest beforehand nor should the digest provide its original value when you pass it through the hash function again.

Now that you got a fair idea about the technical requirements for SHA, you can get into its complete procedure, in the next section.

## Steps in SHA-256 Algorithm

You can divide the complete process into five different segments, as mentioned below:

### Padding Bits

It adds some extra bits to the message, such that the length is exactly 64 bits short of a multiple of 512. During the addition, the first bit should be one, and the rest of it should be filled with zeroes.

### Padding Length

You can add 64 bits of data now to make the final plaintext a multiple of 512. You can calculate these 64 bits of characters by applying the modulus to your original cleartext without the padding.

### Initialising the Buffers:

You need to initialize the default values for eight buffers to be used in the rounds as follows:

You also need to store 64 different keys in an array, ranging from K[0] to K[63]. They are initialized as follows:

Courtesy: SHA-2 (Wikipedia)

### Compression Functions

The entire message gets broken down into multiple blocks of 512 bits each. It puts each block through 64 rounds of operation, with the output of each block serving as the input for the following block. The entire process is as follows:

Courtesy: Medium Article on SHA 256

While the value of K[i] in all those rounds is pre-initialized, W[i] is another input that is calculated individually for each block, depending on the number of iterations being processed at the moment.

### Output

With each iteration, the final output of the block serves as the input for the next block. The entire cycle keeps repeating until you reach the last 512-bit block, and you then consider its output the final hash digest. This digest will be of the length 256-bit, as per the name of this algorithm.

With the SHA 256 algorithm being implemented thoroughly since the early 90s, there are specific applications that you can look into. You will see them in the next section.

## Applications of SHA algorithm

As seen in the image above, the SHA algorithm is being used in a lot of places, some of which are as follows:

- Digital Signature Verification: Digital signatures follow asymmetric encryption methodology to verify the authenticity of a document/file. Hash algorithms like SHA 256 go a long way in ensuring the verification of the signature.

- Password Hashing: As discussed above, websites store user passwords in a hashed format for two benefits. It helps foster a sense of privacy, and it lessens the load on the central database since all the digests are of similar size.

- SSL Handshake: The SSL handshake is a crucial segment of the web browsing sessions, and it’s done using SHA functions. It consists of your web browsers and the web servers agreeing on encryption keys and hashing authentication to prepare a secure connection.

- Integrity Checks: As discussed above, verifying file integrity has been using variants like SHA 256 algorithm and the MD5 algorithm. It helps maintain the full value functionality of files and makes sure they were not altered in transit.

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## How Can Simplilearn Help You?

With hashing and encryption being a staple in today’s digital workspace, it’s no surprise that the demand for cybersecurity professionals has shot through the roof. Apart from cryptography, multiple other avenues in this field are necessary if one wants to pursue a career as a security analyst or network administrator.

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## Conclusion

In today’s lesson on SHA 256 algorithm, you learned the basics of hashing, the applications of hashing, the origin of SHA, its working, and the places this algorithm finds use. Hopefully, this has been an exciting session for you.

Do you have any questions regarding any part of this tutorial? Please let us know your thoughts and questions in the comment section below, and we will have our experts look at it for you.

## FAQs

### How does the SHA256 algorithm work? ›

SHA-256 is a patented cryptographic hash function that **outputs a value that is 256 bits long**. What is hashing? In encryption, data is transformed into a secure format that is unreadable unless the recipient has a key. In its encrypted form, the data may be of unlimited size, often just as long as when unencrypted.

**What are the applications of SHA algorithm? ›**

Secure Hash Algorithm 1, or SHA-1, was developed in 1993 by the U.S. government's standards agency National Institute of Standards and Technology (NIST). It is widely used in security applications and protocols, including **TLS, SSL, PGP, SSH, IPsec, and S/MIME**.

**What is SHA256 algorithm in Blockchain? ›**

What is SHA-256? A secure hashing algorithm or commonly referred to as SHA-256, is **an unkeyed cryptographic hashing function that takes an input of variable length and produces a 256-bit long hash output**.

**How many number of steps SHA256 requires? ›**

Explanation: The number of round computation steps in the SHA-256 algorithm is **64**. 3. In SHA-512, the message is divided into blocks of size ___ bits for the hash computation.

**Is SHA256 easy to crack? ›**

The SHA-256 algorithm is **not yet easily cracked**. Moreover SHA256 algorithm, such as SHA-512 algorithms compared to other secure top model is calculated more quickly is currently one of the most widely used algorithms.

**Why SHA256 is used in Blockchain? ›**

Secure Hashing Algorithm (SHA) -256 is the hash function and mining algorithm of the Bitcoin protocol, referring to the cryptographic hash function that outputs a 256 bits long value. It moderates the creation and management of addresses, and is also used for transaction verification.

**What are the 5 steps that are done in SHA algorithm? ›**

**Step-by-step SHA-256 hash of “hello world” #**

- Step 1 - Pre-Processing # ...
- Step 2 - Initialize Hash Values (h) # ...
- Step 3 - Initialize Round Constants (k) # ...
- Step 4 - Chunk Loop # ...
- Step 5 - Create Message Schedule (w) # ...
- Step 6 - Compression #

**Is SHA-256 still secure? ›**

SHA-256 is not a secure password hashing algorithm. SHA-512 neither, regardless of how good it has been salted.

**Does SHA-256 need a key? ›**

Hash functions like SHA-* **do not need a key**, they just calculate a hash-value from any input.

**Is Sha-256 used in Bitcoin? ›**

En Bitcoin, **SHA-256 is used for the mining process (creation of bitcoins), but also in the process of generating bitcoin addresses**.

### What type of algorithm is SHA256? ›

SHA-256, which stands for secure hash algorithm 256, is a **cryptographic hashing algorithm** (or function) that's used for message, file, and data integrity verification.

**What are the 3 types of crypto algorithm? ›**

**There are three general classes of NIST-approved cryptographic algorithms, which are defined by the number or types of cryptographic keys that are used with each.**

- Hash functions.
- Symmetric-key algorithms.
- Asymmetric-key algorithms.
- Hash Functions.
- Symmetric-Key Algorithms for Encryption and Decryption.

**How long will SHA-256 last? ›**

If you work through the exercise I proposed above, even if you had miners a trillion trillion trillion times faster than the current network, brute-forcing SHA256 would still take you **71430540814238958387154 years**. The Sun is expected to go out in about 5000000000 years.

**How long does SHA-256 take to crack? ›**

Since the attacker's hardware can compute 500 millions of hash values per second, the average time to crack one password is **one second**.

**How much data can SHA-256 hold? ›**

There is technically a limit, but it's quite large. The padding scheme used for SHA-256 requires that the size of the input (in bits) be expressed as a 64-bit number. Therefore, the maximum size is (2^{64}-1)/8 bytes ~= **2'091'752 terabytes**.

**Which SHA is most secure? ›**

Common attacks like brute force attacks can take years or even decades to crack the hash digest, so **SHA-2** is considered the most secure hash algorithm.

**What happens to bitcoin when sha256 is broken? ›**

in this scenario **sha256-based cryptocurrencies will be worthless**. in general: every cryptocurrency and every encryption-system will be worthless when the underlying algorithm (sha2, sha3, aes, ripemd160, whatever) is "broken" by a quantum commputer.

**Is Sha 256 good for passwords? ›**

Salted SHA-256

SHA-256 is part of the SHA-2 set of cryptographic standards. SHA-256 is a general purpose hash and similar to MD5 it was designed to be fast which makes it **a less than ideal choice for a password hashing**. This hash is mainly provided for migration purposes or where login performance is very critical.

**Why is SHA256 irreversible? ›**

SHA256 is a hashing function, not an encryption function. Secondly, since SHA256 is not an encryption function, it cannot be decrypted. What you mean is probably reversing it. In that case, SHA256 cannot be reversed **because it's a one-way function**.

**How is SHA256 checksum calculated? ›**

**You can use Windows Powershell to calculate the SHA-256 checksum for a file.**

- Open Windows Powershell. ...
- Type Get-FileHash followed by a space.
- Drag the downloaded ZIP file onto the Windows Powershell window after the Get-FileHash command. ...
- Press Enter. ...
- Compare the calculated hash value with the original hash value.

### Is it possible to reverse SHA256? ›

SHA256 is a hashing function, not an encryption function. Secondly, since SHA256 is not an encryption function, **it cannot be decrypted**. What you mean is probably reversing it. In that case, SHA256 cannot be reversed because it's a one-way function.

**Is SHA256 still secure? ›**

Predictably, these are also the hashing algorithms that are often used when generating digital signatures and authenticating digital records. The problem is that, while they are all often used to verify data integrity, only SHA-256 is still secure—MD5 and SHA-1 have known vulnerabilities.

**How much data can SHA-256 hold? ›**

There is technically a limit, but it's quite large. The padding scheme used for SHA-256 requires that the size of the input (in bits) be expressed as a 64-bit number. Therefore, the maximum size is (2^{64}-1)/8 bytes ~= **2'091'752 terabytes**.

**Does SHA-256 require a key? ›**

Hash functions like SHA-* **do not need a key**, they just calculate a hash-value from any input.

**How many bytes is a SHA256 hash? ›**

SHA-256 generates an almost-unique 256-bit (**32-byte**) signature for a text. See below for the source code. A hash is not 'encryption' – it cannot be decrypted back to the original text (it is a 'one-way' cryptographic function, and is a fixed size for any size of source text).

**Can we decrypt SHA256 with salt? ›**

Since SHA256 is a hash based on non-linear functions, there is no decryption method. dCode uses word databases whose hash has already been calculated (several million potential passwords) and checks if the hash is known. **If it is not known or combined with salting the decryption will probably fail**.

**What is better than SHA256? ›**

**SHA-3** (and its variants SHA3-224, SHA3-256, SHA3-384, SHA3-512), is considered more secure than SHA-2 (SHA-224, SHA-256, SHA-384, SHA-512) for the same hash length. For example, SHA3-256 provides more cryptographic strength than SHA-256 for the same hash length (256 bits).

**Who created SHA256 algorithm? ›**

The initial version of the SHA-256 algorithm was created by the **US National Security Agency** in the spring of 2002. A few months later, the national metrological University published the newly-announced encryption Protocol in the FIPS PUB 180-2 secure data processing standard adopted at the Federal level.

**What is the most secure hashing algorithm 2022? ›**

Common attacks like brute force attacks can take years or even decades to crack the hash digest, so **SHA-2** is considered the most secure hash algorithm.

**Which SHA algorithm is best? ›**

Probably the one most commonly used is **SHA-256**, which the National Institute of Standards and Technology (NIST) recommends using instead of MD5 or SHA-1. The SHA-256 algorithm returns hash value of 256-bits, or 64 hexadecimal digits.

### Is Bitcoin based on SHA256? ›

En Bitcoin, **SHA-256 is used for the mining process (creation of bitcoins), but also in the process of generating bitcoin addresses**. This is so because of the high level of security it offers.