# init() Creates a SHA1 hash function. ``` init() ``` ## Discussion Initialize a new hash function by calling this method if you want to hash the data iteratively, such as when you don’t have a buffer large enough to hold all the data at once. Provide data blocks to the hash function using the `update(data:)` or [`update(bufferPointer:)`](/documentation/CryptoKit/Insecure/SHA1/update(bufferPointer:)) method. After providing all the data, call [`finalize()`](/documentation/CryptoKit/Insecure/SHA1/finalize()) to get the digest. If your data fits into a single buffer, you can use the `hash(data:)` method instead, to compute the digest in a single call. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)