What is Hashing?

Key Takeaways

• Hashing is a one-way process that converts data into a fixed-length string, ensuring security and data integrity in cybersecurity, database management, and blockchain.
• It’s widely used for password protection, digital signatures, and blockchain security, as it prevents unauthorized access and ensures data remains unchanged.
• Unlike encryption, a hash value cannot be reversed, making it effective for data verification but vulnerable to hash collisions.
• Despite its advantages in security and efficiency, hashing has limitations, including irreversibility, computational costs, and the risk of collisions.

Have you ever wondered how websites remember your login details without ever actually storing your password? Or how the Bitcoin network selects which miner will add new blocks to the blockchain? The answer to both these questions is hashing, a cryptography technique used in cybersecurity, data management, and even cryptocurrency. It converts data into a fixed-length string of characters, ensuring security while enabling efficient data retrieval. 

This article will explore what hashing is, how it works, and its critical role in various industries. 

What Is Hashing?

Hashing is a method of transforming data into a unique, fixed-length string using a mathematical algorithm. This process ensures data integrity and security while allowing for efficient retrieval in various applications. Unlike encryption, which allows data to be decrypted back into its original form, hashing is irreversible.

For example, when you create a password for an online account, the system does not store the password itself. Instead, it generates a hash and saves that. Upon logging in, the system hashes the password that you enter and compares it with the stored hash. If they match, access is granted. As a result, this method protects user data from cyber threats.

How Does Hashing Work?

Hashing works by taking an input (such as a password, document, or file) and running it through a hash function. This function produces a fixed-length output, known as a hash value or digest. No matter the input size, the output always has the same length.

Hash values are used both for accessing data efficiently, and for data security.

Creating a Hash Function Step-by-Step

1. Input Data: A user provides input, such as a password or file.
2. Hash Function Processing: The hash function processes the input using complex mathematical calculations.
3. Fixed-Length Hash Output: The result is a unique string of characters representing the original data.
4. Comparison: The generated hash is compared with a stored hash to verify data integrity.

Let’s say that you hash the word “hello” using the SHA-256 algorithm, you get:

2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824

Even the smallest change, such as capitalizing the first letter to turn it into “Hello”, produces a completely different hash.

185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969

What Are Hash Functions Used For?

Hash values play a crucial role in different fields, from database management to cybersecurity and blockchain technology:

Data Structure

In computer science, hashing finds wide usage in data structures like hash tables. In other words, these tables store and retrieve records efficiently by assigning each value a unique hash key.

Consider, for example, a list of names:

To create an index, called a hash table,for these records, you would apply a formula to each name to produce a unique numeric value. So you might get something like:

Then to search for the record containing Sarah Jones,you just need to reapply the formula, which directly yields the index key to the record. This is much more efficient than searching through all the records till the matching record is found.

Cybersecurity

Hashes play a role in security systems where they’re used to ensure that transmitted messages have not been tampered with. In a network, the sender generates a hash of the message, encrypts it, and sends it with the message itself. The recipient then decrypts both the message and the hash, produces another hash from the received message, and compares the two hashes. If they’re the same, there is a very high probability that the message was transmitted intact.

In cybersecurity, hashing helps protect sensitive information, such as passwords and digital signatures. Storing hashes instead of plaintext passwords prevents hackers from accessing user credentials, even in the case of a data breach.

If a hacker breaches a website’s database, they will only find hashed passwords rather than the actual login details. Without knowing the original password, it is extremely difficult to reverse-engineer the hash.

Blockchain

Similarly, hashing is fundamental in blockchain technology. Here, every block of transactions is secured with a cryptographic hash, thus ensuring that previous data cannot be altered without breaking the entire chain.

Bitcoin transactions use the SHA-256 hash function to create a secure and immutable record of transactions, making blockchain technology tamper-proof and transparent.

What Is a Hash Function?

A hash function is an algorithm that takes an input and produces a fixed-length hash. A good hash function has the following characteristics:

• Deterministic: Entering the same input multiple times should always produce the same output.
• Fast Computation: It quickly generates hashes for any input size.
• Unique Output: Even a minor change in input produces a drastically different hash.
• Irreversible: The original input cannot be derived from the hash.
• Uniform Distribution: Hashes are evenly distributed to prevent clustering in hash tables.

Hash Function Examples

Today, there are many available hash functions but two of them stand out from the rest. These include

• MD5 (Message Digest Algorithm 5): Designed in 1991 and released in 1992, today it’s considered insecure due to vulnerabilities. Despite that, it’s still not uncommon to see MD5.
• SHA-256 (Secure Hash Algorithm 256-bit): With its roots tied to the US National Security Agency, SHA-256 is frequently used in blockchain and password hashing for security. It produces a longer hash than MD5, making it more resistant to hash collisions and other attacks.

Hashing vs. Encryption

Although hashing and encryption both secure data, they serve different purposes.

Hashing

• One-way process: There’s no way to turn the hash back into the original data.
• Uses: Data integrity, password protection, and blockchain security.
• Example: Password hashing in authentication systems.

Encryption

• Two-way process: It’s possible to decrypt the encrypted data with a key.
• Uses: Secure communication, emails, and confidential data exchange.
• Example: AES encryption used in online banking.

Benefits of Hashing

Hashing offers several advantages that make it essential for cybersecurity and data management. These include:

• Enhanced Security: Protects passwords, files, and transactions from unauthorized access.
• Efficient Data Retrieval: Speeds up search operations in databases.
• Data Integrity: Ensures that nobody has tampered with the data.
• Reduces Storage Requirements: Fixed-length hashes take up less space than raw data.

Disadvantages of Hashing

While hashing is powerful, it has its limitations. Some of the drawbacks of hashing are:

• Irreversibility: Once hashed, data cannot be recovered, which may cause issues if data is lost.
• Hash Collisions: Different inputs can sometimes produce the same hash, leading to security vulnerabilities.
• Computational Cost: Strong hash functions require significant processing power.

What Is a Hashing Collision?

A hashing collision is when two different inputs lead to the generation of the same hash. Ideally, a hash function should produce a unique output for every unique input, but due to mathematical constraints, collisions can happen.

For example, MD5 and SHA-1 produced collisions, making them unfit for security applications. At the same time, modern algorithms like SHA-256 and SHA-3 minimize these risks.

Closing Thoughts

The chancces are you use a public network every day without realising – in fact, you’re using one to read this article! From web pages and messaging apps to blockchain technology, all of these involve putting some degree of trust in a network full of other users. Hashing is the backbone of that trust, ensuring the integrity and confidentiality of your data as it travels across a large public network such as the internet. Beyond that, it is also an efficient way of labelling records in a large database so you can retrieve them easily.

Understanding this widely used subcategory of cryptography gives you important insight into the applications you use every day and how they keep your money and data safe.