3. Initiate Pay

Once the merchant request has been verified, this API is used to safely handle payment requests by encrypting card data using AES and RSA encryption.

API Endpoints

Production Endpoint

https://kwpaypg.casheer.com/COFWAY/InitiatePay

Sandbox Endpoint

https://kwpaypgsb.casheer.com/COFWAY/InitiatePay

Sample Request & Response

The following fields ought to be included in the request body:

Sample Request

 "Initiate pay request{
     "ReferenceId" : "xxxxxxxxx",//The validate request response contained a 15-digit reference ID.
     "MerchantId": xxxxxx, //merchant code
     "ECardData" = "encryptedCard", //card data should be encrypted using
      32BIT AES Encryption 
     "ECardKey" = "encryptedKey", // Encrypt the 32 digit AES key using the RSA public key
     "ACS_CallbackURL"= "call back url for 3DS"+ReferenceId   //optional
     }
     
 };

Sample Response

 {
  "errorCode": 0,
  "errorMessgae": "SUCCESS",
  "result": {
    "authentication": {
      "the3Ds1": null,
      "the3Ds2": null,
      "acceptVersions": null,
      "channel": null,
      "purpose": null,
      "redirect": {
        "customized": null,
        "domainName": "ap.gateway.mastercard.com",
        "html": "<div id=\"threedsChallengeRedirect\" xmlns=\"http://www.w3.org/1999/html\" style=\"height: 100vh\"> <form id =\"threedsChallengeRedirectForm\" method=\"POST\" action=\"https://ap.gateway.mastercard.com/acs/mastercard/v2/prompt\" target=\"challengeFrame\"> <input type=\"hidden\" name=\"creq\" value=\"eyJ0aHJlZURTU2VydmVyVHJhbnNJRCI6IjNmN2E4MmVjLTEzZjYtNDg2Ni05ODVjLTlkOTgxZjIzMGQ0OSJ9\" /> </form> <iframe id=\"challengeFrame\" name=\"challengeFrame\" width=\"100%\" height=\"100%\" ></iframe> <script id=\"authenticate-payer-script\"> var e=document.getElementById(\"threedsChallengeRedirectForm\"); if (e) { e.submit(); if (e.parentNode !== null) { e.parentNode.removeChild(e); } } </script> </div>"
      },
      "redirectHtml": null,
      "version": "3DS2",
      "the3Ds": null,
      "method": "OUT_OF_BAND",
      "payerInteraction": null
    }
  }
}

Field Name	Type	Description
ReferenceId	String	15-digit reference id received in the validate requet response
MerchantId	String	Merchant code
ECardData	String	The encrypted card data encrypted using AES encryption with a 32-bit key. Explained below
ECardKey	String	The AES encryption key, encrypted using an RSA public key generated at here
ACS_CallbackURL	String	Explained here

Explanation of the ECardData Encryption Object

The ECardData field in the request is an encrypted representation of the sensitive card details. The following explains the object that is encrypted using AES encryption before being included in the API request:

{
    "CardNumber": "xxxxxxxxxxxxxxxx",//16-digit card number
    "CardName": "John Doe", //Name mentioned on card
    "CardExpiry": "mm/yy", //month/year format
    "CardCVV": "xxx" //3 decimal number
    "CardBrand" :"VISA"
}

Sample code to encrypt ECardData

AES Encryption C#

 
string aesKeyText = "jcIkNa3ybrNVWxe1GSxycA1ru4GoEETO"; // Generate a 32bit random alphanumeric Key
byte[] aesKey = Encoding.UTF8.GetBytes(aesKeyText);
byte[] IV = new byte[16]; // 16-byte IV initialized to zeros

var cardData = new
{
    CardNumber = "XXXXXXXXXXXXXXXXX",
    CardName = "John Doe",
    CardExpiry = "MM/YY",
    CardCVV = "XXX"
};

string serializedCardData = JsonConvert.SerializeObject(cardData);
string encryptedData = EncryptStringToBytes_Aes(serializedCardData, aesKey, IV);



public static string EncryptStringToBytes_Aes(string plainText, byte[] Key, byte[] IV)
{
    
    using (Aes aesAlg = Aes.Create())
    {
        aesAlg.Key = Key;
        aesAlg.IV = IV;
        aesAlg.Mode = CipherMode.CBC;
        aesAlg.Padding = PaddingMode.PKCS7;

        using (var encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV))
        using (var msEncrypt = new MemoryStream())
        {
            using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
            using (var swEncrypt = new StreamWriter(csEncrypt))
            {
                swEncrypt.Write(plainText);
            }
            return Convert.ToBase64String(msEncrypt.ToArray());
        }
    }
}

RSA Encryption C#

string aesKeyText = "jcIkNa3ybrNVWxe1GSxycA1ru4GoEETO"; //AES KEY Used to encrypt the card data
string publicKeys = "RSA Public Key"   //Previously generated merchant keys

// Encrypt the AES key using the RSA public key
string encryptedKey = RSA_Encrypt(aesKeyText, publicKeys);

public string RSA_Encrypt(string textToEncrypt, string publicKeyString)
{
    if (string.IsNullOrWhiteSpace(textToEncrypt)) throw new ArgumentNullException(nameof(textToEncrypt));
    if (string.IsNullOrWhiteSpace(publicKeyString)) throw new ArgumentNullException(nameof(publicKeyString));

    var bytesToEncrypt = Encoding.UTF8.GetBytes(textToEncrypt);

    using var rsa = new RSACryptoServiceProvider(2048);
    try
    {
        rsa.FromXmlString(publicKeyString);
        var encryptedData = rsa.Encrypt(bytesToEncrypt, true);
        return Convert.ToBase64String(encryptedData);
    }
    finally
    {
        rsa.PersistKeyInCsp = false;
    }
}

ACS_CallbackURL

• The provider will handle the 3D Secure callback if it is empty, and the user will be sent to the callback URL that was supplied in step 1. For more info about redirection refer here.

• If provided, the 3D Secure callback will be sent to the merchant's specified URL, and the merchant must call the API at here for further processing.

Response Explaination

Upon receiving the response from the InitiatePay API, the merchant must verify the errorCode to determine the next steps. If the errorCode is 0, indicating a successful initiation, the merchant should parse the result object and render the HTML content provided in result.redirect.html to proceed with the 3DS authentication process.