Swift iOS SSL public key pinning

gistfile1.swift

func connection(connection: NSURLConnection, didReceiveAuthenticationChallenge challenge: NSURLAuthenticationChallenge) {
	if(challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust) {
		var localTrust: Unmanaged<SecTrust>?
		let serverTrust = challenge.protectionSpace.serverTrust!
		let serverPublicKey = SecTrustCopyPublicKey(serverTrust).takeRetainedValue();
		let certificateData = NSData(contentsOfFile: NSBundle.mainBundle().pathForResource("pinning-certificate", ofType: "der")!)
		let localCertificate = SecCertificateCreateWithData(kCFAllocatorDefault, certificateData).takeRetainedValue();
		let policy = SecPolicyCreateBasicX509().takeRetainedValue()

		if SecTrustCreateWithCertificates(localCertificate, policy, &localTrust) == errSecSuccess {
			let localTrustRef = localTrust!.takeRetainedValue()
			let localPublicKey = SecTrustCopyPublicKey(localTrustRef)!.takeRetainedValue();
			if (localPublicKey as AnyObject).isEqual(serverPublicKey as AnyObject) {
				println("trusted")
				return challenge.sender.performDefaultHandlingForAuthenticationChallenge!(challenge)
			}
		}
	}
	println("not trusted")
	return challenge.sender.cancelAuthenticationChallenge(challenge)
}

for swift 3

 func connection(connection: NSURLConnection, didReceiveAuthenticationChallenge challenge: URLAuthenticationChallenge) {
            
    if(challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust) {
        var localTrust: SecTrust?
        let serverTrust = challenge.protectionSpace.serverTrust!
        let serverPublicKey = SecTrustCopyPublicKey(serverTrust)
        let certificateData = NSData(contentsOfFile: Bundle.main.path(forResource: "pinning-certificate", ofType: "der")!)
        let localCertificate = SecCertificateCreateWithData(kCFAllocatorDefault, certificateData!)
        let policy = SecPolicyCreateBasicX509()
        
        if SecTrustCreateWithCertificates(localCertificate!, policy, &localTrust) == errSecSuccess {

            let localPublicKey = SecTrustCopyPublicKey(localTrust!)!
            if (localPublicKey as AnyObject).isEqual(serverPublicKey as AnyObject) {
               print("trusted")
                return challenge.sender!.performDefaultHandling!(for: challenge)
            }
        }
    }
    print("not trusted")
    return challenge.sender!.cancel(challenge)
}