This CreditCard class allows to read thru a standard Near Field Communication (NFC) or Smart Card (PC/SC) reader. Be aware that to read the data stored in the card, you need a compatible reader:
- An ISO 14443-4 Type B for NFC. Keep in mind as well that the antenna and the gain of your NFC reader need to be strong enough to read all kind of cards. Most of the popular PN532 NFC readers that you can find online does not allow to read all kind of card due to this issue
- A smart card reader compatible to read secured card
Your credit card needs to be compatible with wireless payments for NFC reading. It needs to have a chip to be read by a smart card reader.
You will need a reader with an implementation of a WriteRead function from the class CardWriteRead. You will find an example with the PN532 below.
This class has been tested with various American Express, Visa and Mastercard, mainly from Europe.
Some resources to understand how to communicate with a Credit Card and how to get the data out of it:
- The EMV tutorial from the OpenSCDP web site
- A good list of EMV & NFC Tags from EFTLab
- A complete list of APDU response from EFTLab
- A simple TLV parser from emvlab.org
- Book with all the contact card specifications and contactless from EMVCo. Note that those are the official specifications. Main book used for this decoder is the contactless EMV 4.3 book 3.
Here is a full example on how to read a Credit Card using a PN532. As mention above, the quality of your antenna and gain of the antenna may not allow you to read your card even if it's compatible.
static void Main(string[] args)
{
Pn532 pn532 = new Pn532("COM7", LogLevel.None);
ReadCreditCard(pn532);
}
static void ReadCreditCard(Pn532 pn532)
{
byte[] retData = null;
while ((!Console.KeyAvailable))
{
retData = pn532.AutoPoll(5, 300, new PollingType[] { PollingType.Passive106kbpsISO144443_4B });
if (retData is object)
if (retData.Length >= 3)
break;
// Give time to PN532 to process
Thread.Sleep(200);
}
if (retData is null)
return;
// Check how many cards and the type
Console.WriteLine($"Num tags: {retData[0]}, Type: {(PollingType)retData[1]}");
var decrypted = pn532.TryDecodeData106kbpsTypeB(retData.AsSpan().Slice(3));
if (decrypted is object)
{
Console.WriteLine($"{decrypted.TargetNumber}, Serial: {BitConverter.ToString(decrypted.NfcId)}, App Data: {BitConverter.ToString(decrypted.ApplicationData)}, " +
$"{decrypted.ApplicationType}, Bit Rates: {decrypted.BitRates}, CID {decrypted.CidSupported}, Command: {decrypted.Command}, FWT: {decrypted.FrameWaitingTime}, " +
$"ISO144443 compliance: {decrypted.ISO14443_4Compliance}, Max Frame size: {decrypted.MaxFrameSize}, NAD: {decrypted.NadSupported}");
CreditCard creditCard = new CreditCard(pn532, decrypted.TargetNumber);
creditCard.FillCreditCardInfo();
Console.WriteLine("All Tags for the Credit Card:");
DisplayTags(creditCard.Tags, 0);
// Display Log Entries
var format = Tag.SearchTag(creditCard.Tags, 0x9F4F).FirstOrDefault();
if (format is object)
DisplayLogEntries(creditCard.LogEntries, format.Tags);
}
}
static string AddSpace(int level)
{
string space = "";
for (int i = 0; i < level; i++)
space += " ";
return space;
}
static void DisplayTags(List<Tag> tagToDisplay, int levels)
{
foreach (var tagparent in tagToDisplay)
{
Console.Write(AddSpace(levels) + $"{tagparent.TagNumber.ToString("X4")}-{TagList.Tags.Where(m => m.TagNumber == tagparent.TagNumber).FirstOrDefault()?.Description}");
var isTemplate = TagList.Tags.Where(m => m.TagNumber == tagparent.TagNumber).FirstOrDefault();
if ((isTemplate?.IsTemplate == true) || (isTemplate?.IsConstructed == true))
{
Console.WriteLine();
DisplayTags(tagparent.Tags, levels + 1);
}
else if (isTemplate?.IsDol == true)
{
//In this case, all the data inside are 1 byte only
Console.WriteLine(", Data Object Length elements:");
foreach (var dt in tagparent.Tags)
{
Console.Write(AddSpace(levels + 1) + $"{dt.TagNumber.ToString("X4")}-{TagList.Tags.Where(m => m.TagNumber == dt.TagNumber).FirstOrDefault()?.Description}");
Console.WriteLine($", data length: {dt.Data[0]}");
}
}
else
{
TagDetails tg = new TagDetails(tagparent);
Console.WriteLine($": {tg.ToString()}");
}
}
}
static void DisplayLogEntries(List<byte[]> entries, List<Tag> format)
{
for (int i = 0; i < format.Count; i++)
Console.Write($"{TagList.Tags.Where(m => m.TagNumber == format[i].TagNumber).FirstOrDefault()?.Description} | ");
Console.WriteLine();
foreach (var entry in entries)
{
int index = 0;
for (int i = 0; i < format.Count; i++)
{
var data = entry.AsSpan().Slice(index, format[i].Data[0]);
var tg = new TagDetails(new Tag() { TagNumber = format[i].TagNumber, Data = data.ToArray() });
Console.Write($"{tg.ToString()} | ");
index += format[i].Data[0];
}
Console.WriteLine();
}
}You just need to pass a compatible CardWriteRead class and a target number. Note that some readers don't have this nothing, in this case, just ignore this setting.
CreditCard creditCard = new CreditCard(pn532, decrypted.TargetNumber); The FillCreditCardInformation function gets all the public data from your card.
creditCard.FillCreditCardInformation();The Credit Card stores data in Tags. Those Tags have a specific number and data. The data format, the description of those tags are available in the TagList class. You can use it to display those data.
Note as well that a ToString() converter has been implemented. The function in the example above DisplayTags gives an example on how you can display all the Tags and their data.
This Credit Card class allows you to gather all the public information present into your credit card. The class does not implement fully all what is necessary to initiate a payment. Nothing prevent it as all the primary elements are present but you'll need to implement the Authentication.