Hashing is a fundamental technique in cybersecurity. When sending information through an open network, there’s always a risk of bad actors altering the message’s content before it reaches its intended destination. However, decentralized networks, such as blockchain, offer a promising solution. A unique signature is necessary to ensure the authenticity and originality of data sent or received.

But how can one create a unique signature suitable for datasets of varying types and sizes? The answer lies in hash values, which are generated through the hashing process, offering a robust solution to this challenge.

What Is Hashing?

Hashing is a cryptographic process where an input (often called a “message”) of any length is transformed into a fixed-length string of bytes. This is achieved using a mathematical algorithm known as the “Hash Function“. The primary purpose of hashing is to uniquely identify data. The resulting hash value, often just called a “hash”, serves as a digital fingerprint for the input data.

Top 3 Components of Hashing

Understanding the fundamental components of hashing is essential for anyone looking to grasp the intricacies of data structures and algorithms. Here are the top three primary components of hashing:

1. Key: The key is the original piece of data that one wishes to store or retrieve. In the context of data structures like hash tables, the key is used to determine the index where its associated value will be stored. The key is unique, ensuring that each piece of data has a distinct location or reference point within the hash table.
2. Hash Function: This mathematical algorithm accepts the key as input and provides an index where one should store or retrieve the associated value. The primary purpose of the hash function is to distribute the keys uniformly across the hash table, minimizing collisions (situations where two keys produce the same index). A good hash function ensures efficient data retrieval, as it consistently provides a unique index for different keys.
3. Hash Table: Sometimes called a hash map, the hash table is a data structure that implements an associative array. It stores and retrieves data using key-value pairs. The hash function takes the key, processes it, and provides an index in the hash table where the system stores the corresponding value. If designed and managed well, hash tables enable constant-time average complexity for search operations.

SHA 256: The Secure Hash Algorithm

The Secure Hash Algorithm (SHA 256) is one of the most robust cryptographic hash functions currently available. Cryptographic hashes act as digital signatures for data sets. A cryptographic hash function (CHF) generates a cryptographic hash. This specialized function has several properties that make it a secure hash function for cryptography. To consider a cryptographic hash function secure, it must have the following characteristics:

• Quick Computation and Compression: The hash function should be able to quickly calculate and compress data regardless of the input size and produce a fixed-length hash value. Notably, the output’s length shouldn’t correlate with the input’s size.
• Deterministic Nature: The same input data must always produce the same hash value. If the hash value changes for the same data set, verifying data authenticity will be unreliable. However, consistent hash values make it easier to keep track of input data.
• Collision Resistance: It should be difficult or nearly impossible to find two different input data sets that produce the same hash value.
• Pre-Image Resistance: Finding the input data from the output hash value should be computationally hard. This makes it difficult for hackers to reverse the hash value to obtain sensitive information.
• One-Way Functionality (Non-reversibility): The process cannot be reversed to obtain the original input data from the hash value. While old hash functions such as MD5 and SHA1 have become reversible due to increased computing power, advanced cryptographic hash functions like SHA256 and SHA512 remain non-reversible.
• Non-predictable: Neither the input data nor the original message should predict the generated hash value.
• Diffusion or Avalanche Effect: Minor changes in the input data should lead to significant changes in the hash value. Even capitalization or digit changes should result in more than a 50% change in the output hash value.

How Hashing Works in Practical Applications

For instance, in cryptocurrency transactions, hashing ensures the integrity and authenticity of the data being transferred. No matter how long or short the input data is, the hash function will always produce a hash of the same fixed length. Consider the following examples using the MD5 Hash Calculator:

Bitcoin, the leading cryptocurrency, uses the Secure Hash Algorithm (SHA) 256. Regardless of the input data’s size, the SHA-256 algorithm consistently produces a 256-bit long hash. This is particularly useful in transactions where large amounts of data need to be handled. Rather than keeping track of the extensive input data, it is easier to keep track of its hash.

One of the most significant benefits of hashing is its ability to detect even the tiniest change in a file. For instance, a simple letter capitalization will result in a different hash value. This makes it an essential tool for ensuring data integrity and authenticity. It is particularly vital in secure transactions like those carried out with Bitcoin. Can you spot the difference in the hash value of the examples below using the SHA-256 hash calculator:

The change of just one letter in the input produces an entirely different hash value, demonstrating the sensitivity of the hashing process. Additionally, it stays constant no matter how many times someone enters a particular input. If the information or data stays the same, it will produce the same hash value.

This level of rigidity and consistency is one of the backbones of blockchain technology, making data protection and authenticity easy to verify. With this technology, data on the blockchain is immutable, and any tampering by a user or node is easily detected. This is a crucial feature for ensuring the integrity and security of transactions carried out using blockchain.

What Are Hashed Identifiers? An Application of Hashing

Many systems, especially those concerned with privacy, hash raw data such as usernames or email addresses to create unique identifiers. These hashed identifiers protect the original data, ensuring that even if there’s a data breach, the raw data remains uncompromised.

For instance, when a user creates an account on a platform, instead of storing their email address directly, the system might store a hash of the email. When the user logs in, the system hashes the entered email and checks it against the stored hash. This way, even if someone gains unauthorized access to the database, they only see hashed values and not the actual email addresses.

In essence, hashed identifiers serve as a protective layer, ensuring data privacy and security in various applications, from user authentication to data storage.

Conclusion

Cryptographic hash functions can further protect data integrity. If you question the authenticity or receive a different variant of data, you can process all received data through the cryptographic hash function. Then, compare the resulting hash value with the published one.

For example, when Microsoft releases free software available for download from multiple websites, Microsoft isn’t the sole custodian of this software installer. Other developers might modify it. To avoid malware or compromised software installers, a user should generate a hash value for each copy of the software downloaded. They can then compare it with the hash value provided on Microsoft’s official website.

Blocks in a blockchain apply a similar procedure. Each new block stores the hash value of the previous block to maintain the chain and safeguard the integrity of all preceding blocks. If someone alters a block, its hash value changes. This discrepancy means the next block won’t match the altered block because their hash values don’t align. To achieve alignment, one must also modify the subsequent block. However, changing that block also changes its hash value, necessitating changes to the next block, and so on. The same scenario will play out for the hundreds and thousands of blocks on that blockchain (blockchains like Ethereum have millions of blocks). Repeating this process for all linked blocks is practically impossible. 

At their core, hash values might appear straightforward. However, they serve as the backbone of the blockchain system, crucially ensuring data remains intact and resistant to tampering.

Identity.com

Blockchain is the future, and it is impressive to see Identity.com contributing to this desired future through the Solana ecosystem and other Web3 projects. Also, as a member of the World Wide Web Consortium (W3C), the standards body for the World Wide Web.

Identity.com, as a future-oriented company, is an open-source ecosystem providing access to on-chain and secure identity verification for businesses,  giving their customers a hassle-free experience. Our solutions improve the user experience and reduce onboarding friction through reusable and interoperable Gateway Passes. Please refer to our docs about how to help you with identity verification and general KYC processes.