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How to calculate the SHA hash of a String or Data instance

Swift version: 5.2

Paul Hudson    @twostraws   

iOS 13 introduced a new framework called CryptoKit, which adds important cryptographic functionality such as encryption and hashing.

If you want to calculate the hash value of a string you need to convert it to an instance of Data like this:

let inputString = "Hello, world!"
let inputData = Data(inputString.utf8)

You then call the hash(data:) method of whichever kind of hash you want: SHA-256, SHA-384, or SHA-512. For example, if you wanted to calculate the SHA-256 hash of your data you’d use this:

let hashed = SHA256.hash(data: inputData)

Finally, you can print out the textual representation of the hash – what we’d considered the user-facing hash string itself – like this:

print(hashed.description)

Obviously if you have an instance of Data you want to hash, you can put that directly into SHA256.hash(data:).

If you want to get the string of your hash, you should convert using the String(format:) initializer, like this:

let hashString = hashed.compactMap { String(format: "%02x", $0) }.joined()
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