Hash

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.