A hash is a way to turn any piece of data into a short, fixed-size string of characters. This string looks random and unique to the original data. When you start with the same input, you always get the same hash output. If even a tiny detail in the input changes, the hash changes completely, making it look very different from the original.
A hash is created by a hash function. This is a type of process or algorithm that reads your original data, which can be of any size, and produces a concise output that always has the same number of characters. The result is sometimes called a hash value or digest. Because of the way these functions work, it is not possible to reverse the process to get the original data back from the hash.
The unique quality of hashes is that even tiny changes in the input data produce totally different output values. This makes hashes good for checking if data has been changed. If two hashes differ, then something in the input was altered.
In blockchains like Bitcoin and Ethereum, hashes are an everyday part of how the technology works. Each piece of transaction data is turned into a hash to help secure and verify information without revealing the original data itself. This use helps networks confirm data integrity, meaning everyone can check that the data has not been tampered with.
Hash functions also help link blocks of data in a chain. Each block contains the hash of the block before it. Because even small changes to a block would change its hash, this linking makes tampering with the blockchain very difficult.
Hashes are more than just short strings of text. They help protect data in several ways:
These traits make hashing a basic piece of cryptocurrency systems and digital security in general.
In blockchain contexts, you might hear about transaction hashes. These are special hashes that act like unique tags for each transaction on a blockchain. They make it possible to find and track transactions quickly and reliably on public records.
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