Hash
A hash is a digital fingerprint: any data is turned into a fixed string that changes completely with the slightest alteration.
Explained simply
A hash function takes any data, say a whole block with thousands of transactions, and computes a short string from it. The same data always yields the same hash. Change a single comma and the hash looks entirely different.
The original data cannot be recovered from the hash. That makes it suitable as a seal: you can check whether something is unchanged without knowing its content.
From the familiar world
A person's fingerprint: unique, the person cannot be reconstructed from the print, but any deviation is spotted immediately. Or the check digit of your IBAN, only vastly stronger.
An example
On Bitcoin every block points to the hash of the previous one. Anyone wanting to forge an old transaction would have to recompute all subsequent blocks, and do so faster than the entire rest of the network.
Why it matters
Hashes are why a blockchain is tamper-proof and why documents (contracts, certificates, proofs of origin) can be notarised via blockchain without being published.
To pass on
„A hash is a digital fingerprint. Change one letter in the document and the print looks completely different.“
The content of this wiki is for general information and educational purposes only. It does not constitute investment advice, an investment recommendation or tax or legal advice. Digital assets are subject to strong price fluctuations and can lead to losses up to a total loss. Content as of 2026, no guarantee of completeness or timeliness.
21 Oaks Capital GmbH acts as a tied agent exclusively for the account and under the liability of AHP Capital Management GmbH, Weißfrauenstraße 12-16, 60311 Frankfurt am Main, Germany. This wiki is a general information service provided by 21 Oaks Capital GmbH. Its content does not constitute individual investment advice and is not a recommendation by AHP Capital Management GmbH. 21 Oaks Capital GmbH, its affiliated companies, the funds it advises or its employees may hold positions in assets explained in this wiki. The explanations are independent of this; the disclosure is made for reasons of transparency.