What is hashing, and how does it work?

Hashing is a cryptographic process that converts data of any size into a fixed, unique value—the hash value. This hash value acts as a digital fingerprint of the data, guaranteeing its integrity.

Hashing relies on the principle of a one-way function: it’s easy to calculate a hash value from input data, but it’s impossible to reverse the hash value back into the original data. This principle ensures high security.

Using specific hashing algorithms (e.g., SHA-256), the hash value is generated. Regardless of the size of the original data, the hash value always has a constant length. Typically, this value is represented in hexadecimal format—a combination of numbers (0–9) and letters (A–F).

One notable feature of hashing is the avalanche effect: even the smallest change to the input data, such as adding a space, produces a completely different hash value. This makes hashing especially reliable for detecting manipulations.

Here’s an example using the SHA-256 hash algorithm:

• Data: “fidentity” → Hash value: 5a25417fa112c7bc591d7a79a4c1598908e2fe4cb1d73ea2a97b2576df40655a

• Data: “fidentity AG” → Hash value: e753c1e761847c0f88b270602fdbfc900d146a353090d0fd870875bd1f997c4e

These hash values were generated using the hash generator at https://www.hashgenerator.de.

Hashing in everyday life

Hashing is used wherever the integrity of data must be guaranteed. Integrity means that data remains unchanged and in its original form - any deviation or tampering becomes immediately detectable.

Examples of hashing in everyday applications:

• Protecting passwords:
  Hashing converts passwords into unique values that cannot be viewed in plain text, even in the event of a database breach. Only the calculated hash values are stored, ensuring a high level of security. Learn in this article about the 2014 Sony leak why passwords should never be stored in plain text - so they're useless to hackers.

• Securing blockchains:
  Hashing ensures that every transaction in a blockchain remains immutable. Each transaction is documented with a hash value linked to previous transactions, guaranteeing the integrity of the entire blockchain.

• Digital signing: In digital signing, the hash value of a document is calculated and encrypted within the signature. The recipient decrypts the value and compares it to a newly calculated hash value. If the two values match, the document is unchanged, and its integrity is confirmed.

Conclusion

Hashing forms the technological foundation for secure and immutable digital processes. It guarantees data integrity and serves as the basis for trusted applications like blockchain, password protection, and digital signatures.

Modern hash algorithms like SHA3-256 are highly robust and even considered secure against quantum computers. However, the landscape continues to evolve, with new threats requiring continuous adaptation and improvement.

Despite growing challenges, hashing remains a reliable cornerstone that prevents tampering and protects digital processes effectively.

Glossary

• Avalanche Effect:
  A principle of hash algorithms that ensures even minor changes to input data produce a completely different hash value.

• Blockchain:
  A decentralized database technology that uses hash values and cryptography to store data in blocks, linking them into an immutable, transparent chain. Typical applications include cryptocurrencies and tamper-proof records.

• Data Integrity:
  The state in which data remains complete, unchanged, and reliable. It ensures that information remains accurate during storage, transmission, or processing, without manipulation.

• Digital Signature:
  An electronic signature that uses cryptographic methods to guarantee the authenticity and integrity of a document. It links the hash value of the document with the signer’s identity.

• Hash Algorithm:
  A specific process implementing a mathematical hash function that converts data of any size into a fixed, unique value. Examples include SHA-256 and SHA3-256.

• Hash Value:
  A hash value is a digital fingerprint generated from input data using a hash algorithm. It’s unique to the data and ensures its integrity. Even the smallest changes to the data produce a completely new hash value (avalanche effect). A hash value has a fixed length regardless of the input data size (e.g., 256 bits for SHA-256) and cannot be reversed due to the one-way function. Hash values are used in digital signatures, blockchain, and password security to guarantee data remains unchanged.