A hash (or hash value) is the output of a cryptographic function that maps input data of any length to a fixed-length string. Even a minimal change in the input produces a completely different hash value. This makes hashing ideal for integrity verification: you can confirm that a file or message was not altered in transit. Common algorithms include SHA-256 and SHA-3. In your ISMS, hashing plays a central role in protecting the integrity of configuration files, software artifacts, and log data. Hash functions are one-way functions — the original input cannot be reconstructed from the hash value.