How to generate RSA public and private keys using Swift 3?

I create the key pairs of public and private using SecKeyGeneratePair.

ViewController

import UIKit
import Security

class ViewController: UIViewController {

    @IBOutlet weak var textFld: UITextField!
    @IBOutlet weak var encryptedTextFld: UITextView!
    @IBOutlet weak var decryptedTextFld: UITextView!

    var statusCode: OSStatus?
    var publicKey: SecKey?
    var privateKey: SecKey?

    override func viewDidLoad() {
        super.viewDidLoad()

        let publicKeyAttr: [NSObject: NSObject] = [kSecAttrIsPermanent:true as NSObject, kSecAttrApplicationTag:"com.xeoscript.app.RsaFromScrach.public".data(using: String.Encoding.utf8)! as NSObject]
        let privateKeyAttr: [NSObject: NSObject] = [kSecAttrIsPermanent:true as NSObject, kSecAttrApplicationTag:"com.xeoscript.app.RsaFromScrach.private".data(using: String.Encoding.utf8)! as NSObject]

        var keyPairAttr = [NSObject: NSObject]()
        keyPairAttr[kSecAttrKeyType] = kSecAttrKeyTypeRSA
        keyPairAttr[kSecAttrKeySizeInBits] = 2048 as NSObject
        keyPairAttr[kSecPublicKeyAttrs] = publicKeyAttr as NSObject
        keyPairAttr[kSecPrivateKeyAttrs] = privateKeyAttr as NSObject

        statusCode = SecKeyGeneratePair(keyPairAttr as CFDictionary, &publicKey, &privateKey)

        if statusCode == noErr && publicKey != nil && privateKey != nil {
            print("Key pair generated OK")
            print("Public Key: \(publicKey!)")
            print("Private Key: \(privateKey!)")
        } else {
            print("Error generating key pair: \(String(describing: statusCode))")
        }

    }

    @IBAction func encryptPressed(_ sender: Any) {

    }

    @IBAction func decryptPressed(_ sender: Any) {

    }

Then I got the keys like below

Public Key

<SecKeyRef algorithm id: 1, key type: RSAPublicKey, version: 4, block size: 2048 bits, exponent: {hex: 10001, decimal: 65537}, modulus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addr: 0x608000420e80>

Private Key

<SecKeyRef algorithm id: 1, key type: RSAPrivateKey, version: 4, block size: 2048 bits, addr: 0x60000003b960>

But I don't want to generate like above.

I except the keys like below

Public Key

Private Key

How to convert the keys generated by SecKeyGeneratePair to -----BEGIN RSA PUBLIC KEY----- ................ -----END RSA PUBLIC KEY----- format

Solution

Please try this :

let publicKeyAttr: [NSObject: NSObject] = [
            kSecAttrIsPermanent:true as NSObject,
            kSecAttrApplicationTag:"com.xeoscript.app.RsaFromScrach.public".data(using: String.Encoding.utf8)! as NSObject,
            kSecClass: kSecClassKey, // added this value
            kSecReturnData: kCFBooleanTrue] // added this value
let privateKeyAttr: [NSObject: NSObject] = [
            kSecAttrIsPermanent:true as NSObject,
            kSecAttrApplicationTag:"com.xeoscript.app.RsaFromScrach.private".data(using: String.Encoding.utf8)! as NSObject,
            kSecClass: kSecClassKey, // added this value
            kSecReturnData: kCFBooleanTrue] // added this value

var keyPairAttr = [NSObject: NSObject]()
keyPairAttr[kSecAttrKeyType] = kSecAttrKeyTypeRSA
keyPairAttr[kSecAttrKeySizeInBits] = 2048 as NSObject
keyPairAttr[kSecPublicKeyAttrs] = publicKeyAttr as NSObject
keyPairAttr[kSecPrivateKeyAttrs] = privateKeyAttr as NSObject

var publicKey : SecKey?
var privateKey : SecKey?;

let statusCode = SecKeyGeneratePair(keyPairAttr as CFDictionary, &publicKey, &privateKey)

if statusCode == noErr && publicKey != nil && privateKey != nil {
    print("Key pair generated OK")
    var resultPublicKey: AnyObject?
    var resultPrivateKey: AnyObject?
    let statusPublicKey = SecItemCopyMatching(publicKeyAttr as CFDictionary, &resultPublicKey)
    let statusPrivateKey = SecItemCopyMatching(privateKeyAttr as CFDictionary, &resultPrivateKey)

    if statusPublicKey == noErr {
        if let publicKey = resultPublicKey as? Data {
            print("Public Key: \((publicKey.base64EncodedString()))")
        }
    }

    if statusPrivateKey == noErr {
        if let privateKey = resultPrivateKey as? Data {
            print("Private Key: \((privateKey.base64EncodedString()))")
        }
    }
} else {
    print("Error generating key pair: \(String(describing: statusCode))")
}