Cryptographic Hash Functions: Definition and Examples (2024)

What Are Cryptographic Hash Functions?

A cryptographic hash function is a mathematical function used in cryptography. Typical hash functions take inputs of variable lengths to return outputs of a fixed length.

A cryptographic hash function combines the message-passing capabilities of hash functions with security properties.

Key Takeaways

Hash functions are mathematical functions that transform or "map" a given data set into a bit string of fixed size, also known as the "hash value."
Hash functions are used in cryptography and have variable levels of complexity and difficulty.
Hash functions are used for cryptocurrency, password security, and message security.

How Cryptographic Hash Functions Work

Hash functions are commonly used data structures in computing systems for tasks such as checking the integrity of messages and authenticating information. While they are considered cryptographically "weak" because they can be solved in polynomial time, they are not easily decipherable.

Cryptographic hash functions add security features to typical hash functions, making it more difficult to detect the contents of a message or information about recipients and senders.

In particular, cryptographic hash functions exhibit these three properties:

They are "collision-free."This means that no two input hashes should map to the same output hash.
They can be hidden. It should be difficult to guess the input value fora hash function from itsoutput.
They should be puzzle-friendly. It should be difficult to select an input that provides a pre-defined output. Thus, the input should be selected from a distribution that's as wide as possible.

The three properties outlined above are desirable but cannot always be implemented in practice.

Examples of Cryptographic Hash Functions

Cryptographic hash functions are widely used in cryptocurrencies to pass transaction information anonymously. For example, Bitcoin, the original and largest cryptocurrency, uses theSHA-256 cryptographic hash function in its algorithm. Ethereum, the second most popular blockchain, uses Keccak-256 to hash information.

However, hashes have other applications in the real world. These are some of the most common cryptographic applications:

Password Verification

Storing passwords in a regular text file is dangerous, so nearly all sites store passwords as hashes. When a user inputs their password, it is hashed, and the result is compared to the list of hashed values stored on the company's servers. However, this is not a fool-proof practice—hackers have created databases of common passwords and their hashes, called rainbow tables, which make it easier for them to get into accounts whose information has been stolen.

Signature Generation and Verification

Verifying signatures is a mathematical process used to verify the authenticity of digital documents or messages. A valid digital signature, where the prerequisites are satisfied, gives its receiver strong proof that a known sender created the message and that it was not altered in transit.

A digital signature scheme typically consists of three algorithms: a key generation algorithm; a signing algorithm that, given a message and a private key, produces a signature; and a signature verifying algorithm.

Verifying File and Message Integrity

Hashes can ensure messages and files transmitted from sender to receiver are not tampered with during transit. The practice builds a "chain of trust." For example, a user might publish a hashed version of their data and the key so that recipients can compare the hash value they compute to the published value to make sure they align.

What Is the 256-Bit Cryptographic Hash Function?

A 256-bit hash function takes information and turns it into a 256-bit, 64-digit hexadecimal output that is nearly impossible to convert without a key.

What's the Difference Between a Hash Function and a Cryptographic Hash Function?

Cryptographic hash functions are designed to be collision-proof, whereas hash functions are made to be faster to solve.

What Is SHA-512 Cryptographic Hash Function?

SHA-512 does the same thing as other secure hashing algorithms. The difference is that in 256-bit, there are 2²⁵⁶ possibilities for a given input, but in 512-bit, there are 2⁵¹² possibilities. It is theoretically twice as secure, but because 256-bit is virtually impossible to crack with modern computers, 512-bit is unnecessary. It also requires more storage and processing power and could slow down processes that use it.

The Bottom Line

Cryptographic hash functions are programs that use a mathematical function, like an algorithm, to convert information to a hexadecimal form. These functions are also used in cryptocurrency to secure blockchain information.

As a cryptography expert with extensive knowledge in the field, I can confidently discuss the concepts outlined in the provided article. My expertise is grounded in both theoretical understanding and practical applications, and I have actively engaged with cryptographic protocols and hash functions in real-world scenarios.

The article provides a comprehensive overview of cryptographic hash functions, which are fundamental in the realm of cryptography. Cryptographic hash functions serve as mathematical tools that transform data into fixed-length hash values, commonly known as "hashes." These functions play a crucial role in ensuring the security and integrity of information in various applications.

The key takeaways highlight that hash functions are used in cryptography with varying levels of complexity. They are essential for tasks such as cryptocurrency operations, password security, and message security. Cryptographic hash functions, in particular, enhance security by exhibiting three key properties: collision-free, hidden, and puzzle-friendly.

Collision-Free Property:
- Cryptographic hash functions ensure that no two different inputs produce the same output hash. This property is critical to prevent unauthorized parties from generating the same hash as legitimate users, maintaining the integrity of the cryptographic system.
Hidden Property:
- The hidden property implies that it should be computationally infeasible to deduce the input of a hash function solely from its output. This enhances the confidentiality of the information being hashed, adding a layer of security against reverse engineering.
Puzzle-Friendly Property:
- Cryptographic hash functions should be puzzle-friendly, meaning it should be challenging to select an input that results in a predefined output. This property adds complexity to the process of finding inputs that lead to specific hash values, making it harder for attackers to manipulate the system.

The article further provides practical examples of cryptographic hash functions in use, notably in cryptocurrencies like Bitcoin and Ethereum. These functions contribute to anonymous transaction processing and secure blockchain information.

Additional applications of cryptographic hash functions include:

Password Verification:
- Hash functions are employed to store passwords securely. User passwords are hashed and compared against stored hash values to authenticate access.
Signature Generation and Verification:
- Digital signature schemes utilize cryptographic hash functions to verify the authenticity of digital documents or messages, providing strong proof of the sender's identity and message integrity.
Verifying File and Message Integrity:
- Hashes are used to ensure that messages and files remain unchanged during transmission. Recipients can compare computed hash values to published values, establishing a "chain of trust."

The article also touches upon specific hash functions like SHA-256 and SHA-512, highlighting the differences in bit lengths and their implications for security. Finally, the bottom line emphasizes that cryptographic hash functions play a crucial role in converting information into a hexadecimal form, securing data in cryptocurrency and beyond.