---
title: Hash
url: "https://www.unknowngravity.com/en/glosario/hash"
site: Unknown Gravity
published: "2025-06-07T15:11:25+00:00"
modified: "2026-07-15T10:51:28+00:00"
language: en-US
description: "Un Hash It's the result of applying a cryptographic hash function, an algorithm that transforms an arbitrary data entry (of any size) into a fixed-length output (such as 256 bits in the case of…"
section: "Home > Hash"
---

# Hash

GLOSSARY · BLOCKCHAIN & WEB3

A cryptographic function that transforms data of any size into a fixed string of characters, unique for each entry.

WHAT IS IT? · FOR DUMMIES

A **Hash** is like a **digital fingerprint**. Convert any type of information (a text, an image or a transaction) into a **unique and fixed code**. If you change even a comma in the content, the hash changes completely. It is used to ensure that **nothing has been modified**.

WHAT IS IT? · PRO

A **Hash** is the **result of applying a cryptographic hash function**, an algorithm that transforms an arbitrary data entry (of any size) into a **fixed-length output** (such as 256 bits in the case of SHA-256). This output acts as a **unique identifier of the content**, fulfilling three fundamental properties:

1. **Determinism**: the same entry always generates the same hash.
2. **Uniqueness**: it's practically impossible for two different entries to generate the same hash (*collision*).
3. **Irreversibility**: You cannot infer the original entry from the hash.

In blockchain, hashes are used to:

- **Link blocks to each other**, ensuring the integrity of the history (each block contains the hash of the previous block).
- **Verify the authenticity of transactions or smart contracts**.
- **Digitally sign data**, allowing us to validate that they have not been altered.
- **Building Merkle trees**, which make it possible to verify large sets of data efficiently.
- **Generate unique identifiers for tokenized assets, NFTs, users or contracts**.

Common hash functions include **SHA-256** (Bitcoin), **Keccak-256** (Ethereum), **Blake 2**, among others. A small change in the input generates a completely different hash, which guarantees **immutability and resistance to manipulation**.

In legal, cybersecurity and document verification applications, hashes allow **prove the previous existence and the non-alteration of a content**, making them especially useful for certifications, traceability and digital identity systems.

## 01 / Key points

- Convert data into a unique, fixed-size identifier
- Used to verify integrity, link blocks and digitally sign
- It's irreversible: you can't recover the original content from the hash
- Fundamental to the structure of blockchain and smart contracts
- Minor differences in data generate completely different hashes

## 02 / Advantages

- **Guarantees data integrity and authenticity**
- **Very computationally efficient**, even for large volumes of information
- **Resistant to manipulation and attacks if used with good practices**
- **Extensive support in cryptography, blockchain and cybersecurity**
- **Base for structures such as Merkle trees, digital signatures and traceability**

## 03 / Disadvantages

- **Possible theoretical collisions**, although extremely unlikely with safe functions
- **It doesn't protect data on its own**, only verifies its integrity
- **Can be vulnerable if obsolete or poorly implemented hash functions are used**
- **It does not allow you to revert or recover the original content**
- **Requires technical understanding to apply it correctly to critical projects**

RELATED CONCEPTS

[Merkle Tree](/en/glosario/arbol-de-merkle-merkle-tree) [Digital signature](/en/glosario/firma-digital) [Blockchain](/en/glosario/blockchain) [Immutability](/en/glosario/inmutabilidad) [Smart contract](/en/glosario/smart-contract)

KEEP LEARNING

[How to protect your digital assets in the cryptocurrency world](/en/articulos/como-proteger-tus-activos-digitales-criptomonedas) [Decentralization in Blockchain: Transformation, Benefits and Future](/en/articulos/la-importancia-de-la-descentralizacion-en-blockchain) [Smart contracts: good practices that will save you from a hack](/en/articulos/contratos-inteligentes-bien-hechos-buenas-practicas-que-te-salvaran-de-un-hack) [Tokenization without legal problems in Spain and Europe: What you need to know before you start](/en/articulos/tokenizacion-sin-problemas-legales-lo-que-debes-saber-antes-de-empezar) [Blockchain use cases in the supply chain.](/en/articulos/casos-de-uso-de-blockchain-en-la-cadena-de-suministro)

RELATED SERVICES

[Smart contract auditing](/en/servicios/blockchain-security-audits) [Product traceability](/en/servicios/sistema-trazabilidad-de-productos) [Blockchain protocol development](/en/servicios/desarrollo-de-protocolos-blockchain) [Web3 Development](/en/servicios/desarrollo-web3) [Blockchain consulting for companies](/en/servicios/consultoria-blockchain)

[Full glossary](/en/glosario)

This entry is informative. It is not legal, tax or investment advice. The rules cited change: check the current version on [BOE](https://www.boe.es) and [EUR-Lex](https://eur-lex.europa.eu).