NfcReaderLib 1.0.2

NfcReaderLib

Low-level NFC/Smart card utilities library providing PC/SC communication, SL Token generation, and utility functions for card data processing.

?? Installation

Package Manager Console

Install-Package NfcReaderLib -Version 1.0.1

.NET CLI

dotnet add package NfcReaderLib --version 1.0.1

PackageReference

<PackageReference Include="NfcReaderLib" Version="1.0.1" />

?? Target Framework

• .NET Framework 4.7.2

Compatible with:

• .NET Framework 4.7.2+
• .NET Standard 2.0+
• .NET Core 2.0+
• .NET 5+

? Features

Core Functionality

• ?? PC/SC Communication - Low-level smart card reader communication
• ?? SL Token Generation - SHA-256 based secure tokens from ICC certificates
• ?? Card Utilities - Helper functions for card data processing
• ?? Data Formatting - Byte array and hex string conversions
• ??? TLV Support - Tag-Length-Value structure handling

?? Quick Start

using NfcReaderLib;

// Convert hex string to byte array
byte[] data = Util.FromHexString("9F 46 01 02 03");

// Generate SL Token from ICC certificate
var slCard = new SLCard
{
    PAN = "1234567890123456",
    AID = "A0000000031010",
    IccPublicKeyCertificate = iccCertData
};
string token = slCard.GetSLToken2();

// Format card number
string masked = Util.MaskPAN("1234567890123456");
// Output: "1234 56** **** 3456"

// Calculate SHA-256 hash
byte[] hash = Util.CalculateSHA1(data); // Despite name, uses SHA-256

?? Main Classes

SLCard

Purpose: Card model with ICC certificate parsing and SL Token generation

Properties:

• PAN - Primary Account Number
• AID - Application Identifier
• IccPublicKeyCertificate - ICC certificate data (Tag 9F46)
• IccPublicKeyExponent - ICC exponent (Tag 9F47)
• IccPublicKeyRemainder - ICC remainder (Tag 9F48)

Methods:

• GetSLToken2() - Generate SHA-256 based SL Token (space-separated hex format)
• ParseIccCertificate(byte[] data) - Parse multi-line ICC certificate format

Example:

var slCard = new SLCard
{
    PAN = "1234567890123456",
    AID = "A0000000031010",
    IccPublicKeyCertificate = certificateBytes
};

string token = slCard.GetSLToken2();
// Output: "E3 B0 C4 42 98 FC 1C 14 9A FB ... 52 B8 55" (64 hex bytes, space-separated)

Util

Purpose: Utility functions for data conversion and formatting

Key Methods:

Hex Conversions:

• FromHexString(string hex) - Convert hex string to byte array

  byte[] data = Util.FromHexString("9F 46 01 02");
  

• ByteArrayToHexString(byte[] bytes) - Convert byte array to hex string

  string hex = Util.ByteArrayToHexString(data); // "9F460102"
  

• PrettyPrintHex(byte[] data) - Format as space-separated hex

  string pretty = Util.PrettyPrintHex(data); // "9F 46 01 02"
  

PAN Masking:

• MaskPAN(string pan) - Mask card number for privacy

  string masked = Util.MaskPAN("1234567890123456");
  // Output: "1234 56** **** 3456"
  

• MaskCardNumber(string cardNumber, string mask) - Custom masking

  string masked = Util.MaskCardNumber("1234567890123456", "####-##xx-xxxx-####");
  // Output: "1234-56xx-xxxx-3456"
  

Cryptography:

• CalculateSHA1(byte[] data) - SHA-256 hash (note: method name is legacy)

  byte[] hash = Util.CalculateSHA1(certificateData);
  

Data Conversion:

• ByteToInt(byte b) - Convert byte to integer
• ByteToInt(byte first, byte second) - Convert two bytes to integer
• Byte2Short(byte b1, byte b2) - Convert two bytes to short
• HexToAscii(string hexStr) - Convert hex string to ASCII
• NotEmpty(byte[] bytearray) - Check if array has data

String Utilities:

• GetSpaces(int length) - Generate spacing string

ModWinsCard64

Purpose: PC/SC (Personal Computer/Smart Card) wrapper for Windows

Key Methods:

• PC/SC context management
• Card reader enumeration
• APDU command transmission
• ATR (Answer To Reset) reading

Status Word Handling:

• GetScardErrMsg(int retCode) - Get error message for PC/SC return code

Note: This is a low-level class typically used through higher-level wrappers.

?? SL Token Details

What is SL Token?

The SL (Secure Link) Token is a unique cryptographic identifier derived from the card's ICC Public Key Certificate using SHA-256 hashing.

How It Works

ICC Certificate (Tag 9F46) ? SHA-256 Hash ? Space-Separated Hex ? SL Token

Example:

Input:  ICC Certificate (128-248 bytes)
Output: "E3 B0 C4 42 98 FC 1C 14 9A FB F4 C8 99 6F B9 24 27 AE 41 E4 64 9B 93 4C A4 95 99 1B 78 52 B8 55"

Properties

? Unique - Each card generates a unique token
? Consistent - Same card always produces the same token
? Secure - One-way hash, cannot be reversed
? Privacy-Friendly - No PAN or sensitive data exposed
? Format - 64 bytes as space-separated hex (191 characters)

Use Cases

• ?? Loyalty program card identification
• ?? Card binding to user accounts
• ?? Transaction correlation
• ?? Duplicate card detection
• ?? Analytics without storing sensitive data

??? Advanced Usage

Multi-Line ICC Certificate Parsing

The SLCard class handles multi-line certificate formats automatically:

string certData = @"Cert: 9F4681...
Exp: 03
Rem: 12345...";

var slCard = new SLCard
{
    PAN = "1234567890123456",
    AID = "A0000000031010"
};

// Parse multi-line format
string[] lines = certData.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
foreach (string line in lines)
{
    if (line.StartsWith("Cert:"))
        slCard.IccPublicKeyCertificate = Util.FromHexString(line.Substring(5));
    else if (line.StartsWith("Exp:"))
        slCard.IccPublicKeyExponent = Util.FromHexString(line.Substring(4));
    else if (line.StartsWith("Rem:"))
        slCard.IccPublicKeyRemainder = Util.FromHexString(line.Substring(4));
}

string token = slCard.GetSLToken2();

Custom Hex Formatting

byte[] data = new byte[] { 0x9F, 0x46, 0x01, 0x02 };

// Standard hex string (no spaces)
string standard = Util.ByteArrayToHexString(data); // "9F460102"

// Pretty print (with spaces)
string pretty = Util.PrettyPrintHex(data); // "9F 46 01 02"

// Parse back
byte[] parsed = Util.FromHexString(pretty);

PAN Masking Patterns

// Standard masking (first 6 + last 4)
string pan1 = Util.MaskPAN("1234567890123456"); 
// "1234 56** **** 3456"

// Custom masking
string pan2 = Util.MaskCardNumber("1234567890123456", "####-####-####-####");
// "1234-5678-9012-3456"

string pan3 = Util.MaskCardNumber("1234567890123456", "####-##xx-xxxx-####");
// "1234-56xx-xxxx-3456"

?? Dependencies

• System.Security.Cryptography.Algorithms (v4.3.1) - SHA-256 hashing

?? Requirements

• .NET Framework 4.7.2 or later
• Windows 7 or later (for PC/SC support)

?? Documentation

For complete documentation and usage examples, visit:

• GitHub Repository
• NuGet Package

?? Related Packages

• EMVCard.Core - High-level EMV card reading library (depends on NfcReaderLib)

?? License

Copyright � Johan Henningsson 2026

This project is licensed under the MIT License.

?? Author

Johan Henningsson

• GitHub: @johanhenningsson4-hash
• Repository: EMVReaderSL

?? Acknowledgments

• EMV specifications by EMVCo
• PC/SC Workgroup
• .NET Cryptography API

Made with ?? by Johan Henningsson | 2008-2026

? Star this package on GitHub if you find it useful!