Cryptographic Hash
SHA-3 (Secure Hash Algorithm 3) 1
SHA-256 (Secure Hash Algorithm 256) 2
How Hashes Are Used in Blockchain 3
What Is a Cryptographic Hash?
A cryptographic hash is a unique code made up of letters and numbers. In computing, it works much like a digital fingerprint. No matter what type or size of data you start with, a hash can be created from it, and depending on the algorithm used, the result will always be the same length.
For example, here’s what the word “hello” looks like when hashed using the SHA-256 algorithm:
2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824
Even if you were to hash an entire novel using SHA-256, the result would still be exactly the same number of characters.
Hash Algorithms
Hash algorithms are programs that can encrypt any kind of digital data into a hash.
Here are some of the most popular hash algorithms:
MD5 (Message Digest 5)
MD5 used to be widely used for hashing digital signatures and passwords. Although it’s still faster than newer algorithms like SHA-3 or SHA-256, it is now considered outdated because it can be compromised. An MD5 hash is 128 bits long (16 bytes), which equals 32 characters in hexadecimal form.
SHA-3 (Secure Hash Algorithm 3)
SHA-3 is a more secure alternative to MD5. It was developed to overcome some of the weaknesses of earlier SHA versions. One major advantage is its flexibility, it can produce hash lengths of 56, 64, 96, or 128 bits.
SHA-256 (Secure Hash Algorithm 256)
SHA-256 turns any input into a 256-bit hash, which equals 64 characters. This algorithm is widely used in blockchain technology. For example, Bitcoin uses SHA-256 to secure its transactions and blocks.
In general, the longer a hash is (in bits or characters), the stronger it is. A longer hash is harder to generate and much harder to reverse-engineer, which makes it more resistant to hacking attempts.
Why Are Hashes Important?
Hashes have some special features that make them essential for securing data on the blockchain:
- One-way Function: It’s easy to create a hash from any kind of data, but it’s nearly impossible to turn a hash back into the original data.
- Collision Resistance: Two different pieces of data should never produce the same hash. The more bits a hash algorithm uses, the better it resists collisions.
- Fast Generation: A hash can be created instantly from any kind of input.
- Sensitive to Changes: Even the smallest change in the input data will result in a completely different hash.
How Hashes Are Used in Blockchain
Since encryption is one of the foundations of blockchain, hash algorithms – and the hashes they generate – play a crucial role in the system’s operation. These algorithms are responsible for creating the hashes for transactions and blocks.
The blocks in a blockchain are connected using hashes. If someone tries to change the data in a block, the hash of that block would change as well. However, the next block still contains the original hash, which immediately reveals the inconsistency. This mismatch is a red flag for all validating nodes on the network and signals that someone has attempted to tamper with the data.
A cryptographic hash is a powerful data encryption tool that assigns a unique “fingerprint” to any piece of information. On the blockchain, hashes act like the glue that holds the blocks together and protects the data from tampering.
While the hash creation process happens quietly in the background during blockchain use, it plays a key role in maintaining the security and transparency of the entire system.
