swift-crypto-example.swift

import Foundation
import Crypto // https://github.com/apple/swift-crypto

extension Data {
    struct HexEncodingOptions: OptionSet {
        let rawValue: Int
        static let upperCase = HexEncodingOptions(rawValue: 1 << 0)
    }

    func hexEncodedString(options: HexEncodingOptions = []) -> String {
        let format = options.contains(.upperCase) ? "%02hhX" : "%02hhx"
        return map { String(format: format, $0) }.joined()
    }
}
// Data dump methods

let bobPrivateKey = Curve25519.KeyAgreement.PrivateKey()
let alicePrivateKey = Curve25519.KeyAgreement.PrivateKey()

let bobPublicKey = bobPrivateKey.publicKey
let alicePublicKey = alicePrivateKey.publicKey

// Bob sends his Public key to Alice
print(bobPublicKey.rawRepresentation.base64EncodedString())

do {
		// Each party creats a shared secret from each others public keys
    let shared_secret_bob = try bobPrivateKey.sharedSecretFromKeyAgreement(with: alicePublicKey)
    let shared_secret_alice = try alicePrivateKey.sharedSecretFromKeyAgreement(with: bobPublicKey)

    // Bob creates shared key
    let bobs_key = shared_secret_bob.x963DerivedSymmetricKey(using: Crypto.SHA512.self , sharedInfo: bobPublicKey.rawRepresentation, outputByteCount: 16)
    let message = "Testing123..."
		// and encripts some data with it
    let sealedMessage = try AES.GCM.seal(message.data(using: .utf8)!, using: bobs_key)

    print(sealedMessage.ciphertext.hexEncodedString(options: [.upperCase]))


    // Alice creates the same shared key
    let alice_key = shared_secret_alice.x963DerivedSymmetricKey(using: Crypto.SHA512.self , sharedInfo: bobPublicKey.rawRepresentation, outputByteCount: 16)

		// and decripts encrypted message with it
    let unsealed_message = try AES.GCM.open(sealedMessage, using: alice_key);
	
    let string = String.init(data: unsealed_message, encoding: .utf8) ?? "Error"

		// Get the decrypred message
    print(string)
	
} catch {
    print(error.localizedDescription)
}