What is a cryptographic hash?

A cryptographic hash is a function that enables miners to validate a block on the blockchain. Every block has a limit, so once a block is full after nodes verify all transactions, an encrypted alphanumeric code called ‘hash’ is generated. Miners have to randomly guess the code to validate the block.

A hash enables users to store passwords in a database securely. It also ensures the integrity and authentication of data. Furthermore, it facilitates scalability by organizing content and files to increase efficiency. While hashes generally have a fixed length, they become more complex as time passes, making the guessing game even harder.

What are cryptographic hash functions?

Essentially, a hash function performs core cryptographic operations called hashing to make sure that the hash keeps the network secure. In other words, a hash function is a cryptographic algorithm that picks inputs of any size and converts them into a unique output of a fixed length. The output is known as a hash digest, hash value, or hash code, which is also the unique identifier.

Hash functions are dynamic identifiers of data, ensuring that the data is not altered or tampered with. Hash does a thorough check to ascertain that no two pieces of data have the same hash digest, and in case of any changes, the hash digest changes as well.

In other words, hashing is a way to ensure that any data you send reaches your recipient intact and unaltered. Hashing performs this task by inputting plaintext data and using mathematical algorithms to generate an encrypted output.

Confused? Let us understand this better with the help of a relatable example from our regular banking experience. When you opened a bank account for the first time, the banker would have asked you to set a password to secure your account. Now, that banker or even the bank does not know your password. They basically run your password through a hashing algorithm and then save the hash as your password. Whenever you log in to your account, the bank’s system compares the password you enter with the hash it has saved, and if the two match, you get to access your bank account.

Examples of cryptographic hash functions

Cryptographic hash functions are used to clear anonymous transactions on the blockchain. For example, the Hashcash (SHA-256) is the proof of work function that Bitcoin miners utilize to randomly guess the alphanumeric code or hash, which will eventually add the block to the blockchain. Hash functions are of two types: Secure Hash Function and Message Digest 5.

Secure Hash Algorithm (SHA)

Secure Hash Function (SHA) comprises four SHA functions — SHA-0, SHA-1, SHA-2, and SHA-3.

While the original version of SHA-0 is a 160-bit hash function, it wasn’t widely accepted. Following this, SHA-1 was designed, which was used extensively. It was employed in several popular applications and protocols, including Secure Socket Layer (SSL) security. However, it was discovered that SHA-1 collisions could be deciphered within a practical time frame, raising concerns about its long-term use case.

Enter the SHA-2 algorithm, which came in four variants — SHA-224, SHA-256, SHA-384, and SHA-512. These were categorized based on the number of bits in their hash value. Thankfully, no successful attacks have yet been reported on the SHA-2 hash function. Nevertheless, the SHA-2 core design still follows SHA-1, prompting the US National Institute of Standards and Technology (NIST) to call for new competitive hash function designs. Thus emerged the SHA-3 algorithm. In October 2012, the NIST selected the Keccak algorithm as the new SHA-3 standard.

Message Digest 5 (MD5)

MD5 generates a 128-bit string value as the hash value and is used to verify data integrity. In the MD family, MD5 is the most widely used hash function. Its digests were widely used in the software world to ensure the integrity of transferred files. However, even MD5 found collisions when an analytical attack was reported within an hour of using a computer cluster.

Features of hash functions in crypto

In cryptography, hash functions perform three important tasks.

Digital signature generation and verification

Digital signatures in cryptography are used to verify the authenticity and integrity of data. The Digital Signature Standard (DSS), a Federal Information Processing Standard (FIPS), provides a list of algorithms that are used to safely generate digital signatures. Under this standard, Secure Hash Algorithms (SHAs) are used to authenticate electronic documents.

Authenticating data integrity

Hash functions are also used to ensure that data transmitted from a sender to the receiver are not tampered with during transit. If you apply a hash function to data, it informs the recipient if the message has been altered. This is important as even the smallest of changes to a message will lead to the creation of an entirely new hash value.

Verify and store passwords

Storing plaintext passwords on a public server leaves your information vulnerable to cyber attacks. Hence, websites hash passwords to generate hash values, which is what they store. However, just hashing is not enough to securely store passwords from exploits like brute force attacks, where an attacker uses a trial-and-error method to crack the password.

An essential ingredient called “salt” is often added to enhance security. “Salt” is a dynamic, random number applied to plaintext passwords before hashing them. Essentially, it adds another layer of security, protecting passwords from password-cracking methods like rainbow table attacks.

Conclusion

In the fast-evolving world of crypto, cryptographic hash functions perform the important security check function. They take plaintext data, run it through a mathematical process called a hashing algorithm, and give out a hash value of a fixed length. With the use of hash, it is easy to spot manipulated data, as even a minute alteration can change the hash value entirely.

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