How to decrypt payment token ?

Hi Guys,

I'm integrating Apple Pay but I can't decrypt Payment Token because I don't know where private key is

I'm using this code

https://github.com/PayU-EMEA/apple-pay

My error:

Decoding failed: 

Can't derive secret

or

Decoding failed: 

Unable to decrypt or to verify the tag.

When I test with demo code, it is working fine:

Decoded token is: 

object(PayU\ApplePay\Decoding\ApplePayPaymentData)#20 (9) {
  ["version":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  int(1)
  ["applicationPrimaryAccountNumber":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  string(16) "5204242750270010"
  ["applicationExpirationDate":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  string(6) "190731"
  ["currencyCode":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  string(3) "643"
  ["transactionAmount":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  int(100000)
  ["deviceManufacturerIdentifier":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  string(12) "050110030273"
  ["paymentDataType":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  string(8) "3DSecure"
  ["onlinePaymentCryptogram":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  string(28) "AOm+7lPDSbobAGVT7hmNAoABFA=="
  ["eciIndicator":"PayU\ApplePay\Decoding\ApplePayPaymentData":private]=>
  NULL
}

I think my private key is wrong

Can you help me to find the private key ?

Thank you !