ChaChaPoly encryption in Swift with CryptoKit

ChaChaPoly_Encryption.playground

import Foundation
import CryptoKit

extension SymmetricKey {
    init?(base64EncodedString: String) {
        guard let data = Data(base64Encoded: base64EncodedString) else {
            return nil
        }

        self.init(data: data)
    }
    
    func serialize() -> String {
        return self.withUnsafeBytes { body in
            Data(body).base64EncodedString()
        }
    }
}

var encKey: String? = nil // Change this if you have an existing key you want to use.
var valuesToBeEncrypted = [String: String]() // Leave this alone.

// Append values to be encrypted here.
valuesToBeEncrypted["value1"] = "secret1"
valuesToBeEncrypted["value2"] = "secret2"
valuesToBeEncrypted["value3"] = "secret3"

// Don't touch
let symKey = if encKey == nil { SymmetricKey(size: .bits256) } else { SymmetricKey(base64EncodedString: encKey!)! }
var encValues = [String: String]()

print("Key: \(symKey.serialize())")
for (key, value) in valuesToBeEncrypted {
    let encryptedValue = try! ChaChaPoly.seal(value.data(using: .utf8)!, using: symKey).combined
    encValues[key] = encryptedValue.base64EncodedString()

    print("Encrypted \(key) (\(value)): \(encryptedValue.base64EncodedString())")
}

// Example of how to decode these values
print("-- VALIDATION --")
for (key, value) in encValues {
    guard let data = Data(base64Encoded: value) else {
        print("Failed to initialize data for \(key)")
        continue
    }
    
    if let sealedBox = try? ChaChaPoly.SealedBox(combined: data) {
        if let decryptedData = try? ChaChaPoly.open(sealedBox, using: symKey) {
            print("Decrypted \(key) (\(value)): \(String(data: decryptedData, encoding: .utf8)!)")
        } else {
            print("Failed to decrypt value for \(key)")
            continue
        }
    }
}