Encrypt/decrypt a string with code-generated RSA public/private keys in Swift

The example below shows how to:

- generate private and public RSA keys in Swift.
- encrypt and decrypt a string in Swift.

The Xcode used with this example is version 7.2 (Swift 2.1.1).

1. Modify ViewController.swift as:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {

        super.viewDidLoad()

        

        //Generation of RSA private and public keys

        let parameters: [String: AnyObject] = [

            kSecAttrKeyType as String: kSecAttrKeyTypeRSA,

            kSecAttrKeySizeInBits as String: 1024

        ]

        

        var publicKey, privateKey: SecKey?

        SecKeyGeneratePair(parameters, &publicKey, &privateKey)

        

        //Encrypt a string with the public key

        let message = "This is my message."

        let blockSize = SecKeyGetBlockSize(publicKey!)

        var messageEncrypted = [UInt8](count: blockSize, repeatedValue: 0)

        var messageEncryptedSize = blockSize

        var status: OSStatus!

        

        status = SecKeyEncrypt(publicKey!, SecPadding.PKCS1, message, message.characters.count, &messageEncrypted, &messageEncryptedSize)

        

        if status != noErr {

            print("Encryption Error!")

            return

        }

        

        //Decrypt the entrypted string with the private key

        var messageDecrypted = [UInt8](count: blockSize, repeatedValue: 0)

        var messageDecryptedSize = messageEncryptedSize

        

        status = SecKeyDecrypt(privateKey!, SecPadding.PKCS1, &messageEncrypted, messageEncryptedSize, &messageDecrypted, &messageDecryptedSize)

        

        if status != noErr {

            print("Decryption Error!")

            return

        }

        

        print(NSString(bytes: &messageDecrypted, length: messageDecryptedSize, encoding: NSUTF8StringEncoding)!)

    }

    override func didReceiveMemoryWarning() {

        super.didReceiveMemoryWarning()

    }

}

2. Result:

This is my message.

References:
Apple's document: Certificate, Key, and Trust Services Reference
SecKeyGeneratePair in Swift
Encrypt/decrypt a string with public/private keys imported from PEM files (Swift)

Study Raspberry Pi blog:
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