emvpboc,金融系统中PBOC/EMV的TLV的算法实现（含C++/C#）

TLV即Tag-Length-Value，常在IC卡与POS终端设备中通过这样的一个应用通信协议进行数据交换。在金融系统以及认证中，PBOC以及EMV的认证规范文档上面也有对TLV做了一些说明，由于认证规范都是英文文档，所以有些人可能不易于理解。首先我先介绍下什么是TLV，TLV的用途是什么，以及如何实现它的打包解包算法。
金融系统中的TLV是BER-TLV编码的一个特例编码规范，而BER-TLV是ISO定义中的规范。在TLV的定义中，可以知道它包括三个域，分别为：标签域（Tag），长度域（Length），内容域（Value）。这里的长度域的值实际上就是内容域的长度。
其实，在BER编码的方式有两种情况，一种是确定长度的方式，一种是不确定长度的方式，而金融TLV选择了确定长度的方式，这样在设备之间的数据传输量上就可以减少。
Tag域说明：
先来看下TLV的Tag是如何编码的，先看下图：

这张图说明了Tag域第一个字节的编码格式。其中b8-b1代表1个字节中的8个位。
其中b8,b7代表数据的类别。根据2个位的组合，有四种类别：通用类别，应用类别，上下文语境类别，专用类别。这个主要用于在于终端设备交互的时候，确定数据处理的类型。
b6代表的是数据元结构，也就是说它是属于简单数据元结构，还是属于结构（复合）数据元结构。当b6为1的时候，就需要后续的字节进行扩展。也就是说复合的TLV中，value域里也包含一个或多个TLV，这个稍后接着介绍。
当b5-b1代表串行号，当5个位都为1时，需要将tag域扩展到下一个字节中，也就是Tag占2个字节；而当5个位都不全为1时，该Tag域就只占1个字节。
现在，看下b5-b1：11111的情况：

从图中我们看到BER-TLV编码中，当b8为1时，Tag还需要有后续字节，直到b8为0为止。从EMV文档中的说明，Tag最多只占用2个字节，所以这样就相对比较简单一些了。当b8为0时，该Tag域结束，总共就占用2个字节。
Length域说明：
在文档中没有图片叙述，我自绘一个：

当b8为0时，该字节的b7-b1作为value域的长度；当b8为1时，b7-b1作为后续字节的长度，也就是说，例如有这样一个值：10000011，代表后续还有3个字节作为value域的长度（本字节不算，本字节变为作为一个Length的索引）。3个字节代表value的长度，意味着什么呢，意味着内容的长度当需要很大的时候，字节的位数就会跟着越高，3个字节就代表最大可以有256*256*256的长度。
Value域说明：
也是分成两种情况考虑，就是前面说到的Tag分成两个数据元结构，一种是简单数据元结构，一种是复合数据元架构：
先来看看简单数据元结构：

Tag就是Tag,没有子标签Tag，基本结构就是T-L-V。
再看下符合数据元结构：

后面的Value说明：Primitive or constructed BER-TLV data object number，包含一个简单数据元结构或者也可以是一个符合数据元结构。这样可以看出，算法中必须要实现Tag的嵌套功能，递归算法不可少。
算法实现：
根据以上的说明现在来实现它的打包解包的算法（打包的目的是将一个从终端上发的请求数据——字节数组，构造成一系列的TLV结构实体；解包的目的刚好相反，就是将TLV结构实体解析成字节数组，然后通过IC卡发送到终端上）。
首先定义一个TLV结构实体：
// TLV结构体 struct TLVEntity { unsigned char* Tag; //标记 unsigned char* Length; //数据长度 unsigned char* Value; //数据 unsigned int TagSize; //标记占用字节数 unsigned int LengthSize; //数据长度占用字节数 TLVEntity* Sub_TLVEntity; //子嵌套TLV实体 };
其中TagSize代表Tag字段的字节长度，LengthSize代表Length的字节长度，这里的Length记住要使用char*，由于前面说过，Length可能包含多个字节，通过多个字节确定Value域的长度，Sub_TLVEntity作为子嵌套的TLV结构体。 定义一个TLVPackage的打包类：
TLVPackage.h：
// TLV打包类 class TLVPackage { public: TLVPackage(); virtual ~TLVPackage(); //构造TLV实体 static void Construct(unsigned char* buffer, unsigned int bufferLength, TLVEntity* tlvEntity, unsigned int& entityLength, unsigned int status=0); //解析TLV字节数组 static void Parse(TLVEntity* tlvEntity, unsigned int entityLength, unsigned char* buffer, unsigned int& bufferLength); };
具体方法实现：
// 构造TLV void TLVPackage:: Construct( unsigned char* buffer, unsigned int bufferLength, TLVEntity* tlvEntity, unsigned int& entityLength, unsigned int status ) { int currentTLVIndex = 0; int currentIndex = 0; int currentStatus = 'T'; //状态字符 unsigned long valueSize = 0; while(currentIndex < bufferLength) { switch(currentStatus) { case 'T': valueSize = 0; //判断是否单一结构 if((status == 1 && buffer[currentIndex] & 0x20) != 0x20) { tlvEntity[currentTLVIndex].Sub_TLVEntity = NULL; //单一结构时将子Tag置空 //判断是否多字节Tag if((buffer[currentIndex] & 0x1f) == 0x1f) { int endTagIndex = currentIndex; while((buffer[++endTagIndex] & 0x80) == 0x80); //判断第二个字节的最高位是否为1 int tagSize = endTagIndex - currentIndex + 1; //计算Tag包含多少字节 tlvEntity[currentTLVIndex].Tag = new unsigned char[tagSize]; memcpy(tlvEntity[currentTLVIndex].Tag, buffer + currentIndex, tagSize); tlvEntity[currentTLVIndex].Tag[tagSize] = 0; tlvEntity[currentTLVIndex].TagSize = tagSize; currentIndex += tagSize; } else { tlvEntity[currentTLVIndex].Tag = new unsigned char[1]; memcpy(tlvEntity[currentTLVIndex].Tag, buffer + currentIndex, 1); tlvEntity[currentTLVIndex].Tag[1] = 0; tlvEntity[currentTLVIndex].TagSize = 1; currentIndex += 1; } } else { //判断是否多字节Tag if((buffer[currentIndex] & 0x1f) == 0x1f) { int endTagIndex = currentIndex; while((buffer[++endTagIndex] & 0x80) == 0x80); //判断第二个字节的最高位是否为1 int tagSize = endTagIndex - currentIndex + 1; //计算Tag包含多少字节 tlvEntity[currentTLVIndex].Tag = new unsigned char[tagSize]; memcpy(tlvEntity[currentTLVIndex].Tag, buffer + currentIndex, tagSize); tlvEntity[currentTLVIndex].Tag[tagSize] = 0; tlvEntity[currentTLVIndex].TagSize = tagSize; currentIndex += tagSize; } else { tlvEntity[currentTLVIndex].Tag = new unsigned char[1]; memcpy(tlvEntity[currentTLVIndex].Tag, buffer + currentIndex, 1); tlvEntity[currentTLVIndex].Tag[1] = 0; tlvEntity[currentTLVIndex].TagSize = 1; currentIndex += 1; } //分析SubTag int subLength = 0; unsigned char* temp; if((buffer[currentIndex] & 0x80) == 0x80) { for (int index = 0; index < 2; index++) { subLength += buffer[currentIndex + 1 + index] << (index * 8); //计算Length域的长度 } temp = new unsigned char[subLength]; memcpy(temp, buffer + currentIndex + 3, subLength); } else { subLength = buffer[currentIndex]; temp = new unsigned char[subLength]; memcpy(temp, buffer + currentIndex + 1, subLength); } temp[subLength] = 0; //memcpy(temp, buffer + currentIndex + 1, subLength); unsigned int oLength; tlvEntity[currentTLVIndex].Sub_TLVEntity = new TLVEntity[1]; Construct(temp, subLength, tlvEntity[currentTLVIndex].Sub_TLVEntity, oLength); } currentStatus = 'L'; break; case 'L': //判断长度字节的最高位是否为1，如果为1，则该字节为长度扩展字节，由下一个字节开始决定长度 if((buffer[currentIndex] & 0x80) != 0x80) { tlvEntity[currentTLVIndex].Length = new unsigned char[1]; memcpy(tlvEntity[currentTLVIndex].Length, buffer + currentIndex, 1); tlvEntity[currentTLVIndex].Length[1] = 0; tlvEntity[currentTLVIndex].LengthSize = 1; valueSize = tlvEntity[currentTLVIndex].Length[0]; currentIndex += 1; } else { //为1的情况 unsigned int lengthSize = buffer[currentIndex] & 0x7f; currentIndex += 1; //从下一个字节开始算Length域 for (int index = 0; index < lengthSize; index++) { valueSize += buffer[currentIndex + index] << (index * 8); //计算Length域的长度 } tlvEntity[currentTLVIndex].Length = new unsigned char[lengthSize]; memcpy(tlvEntity[currentTLVIndex].Length, buffer + currentIndex, lengthSize); tlvEntity[currentTLVIndex].Length[lengthSize] = 0; tlvEntity[currentTLVIndex].LengthSize = lengthSize; currentIndex += lengthSize; } currentStatus = 'V'; break; case 'V': tlvEntity[currentTLVIndex].Value = new unsigned char[valueSize]; memcpy(tlvEntity[currentTLVIndex].Value, buffer + currentIndex, valueSize); tlvEntity[currentTLVIndex].Value[valueSize] = 0; currentIndex += valueSize; //进入下一个TLV构造循环 currentTLVIndex += 1; currentStatus = 'T'; break; default: return; } } entityLength = currentTLVIndex; } // 解析TLV void TLVPackage::Parse( TLVEntity* tlvEntity, unsigned int entityLength, unsigned char* buffer, unsigned int& bufferLength ) { int currentIndex = 0; int currentTLVIndex = 0; unsigned long valueSize = 0; while(currentTLVIndex < entityLength) { valueSize = 0; TLVEntity entity = tlvEntity[currentTLVIndex]; memcpy(buffer + currentIndex, entity.Tag, entity.TagSize); //解析Tag currentIndex += entity.TagSize; for (int index = 0; index < entity.LengthSize; index++) { valueSize += entity.Length[index] << (index * 8); //计算Length域的长度 } if(valueSize > 127) { buffer[currentIndex] = 0x80 | entity.LengthSize; currentIndex += 1; } memcpy(buffer + currentIndex, entity.Length, entity.LengthSize); //解析Length currentIndex += entity.LengthSize; //判断是否包含子嵌套TLV if(entity.Sub_TLVEntity == NULL) { memcpy(buffer + currentIndex, entity.Value, valueSize); //解析Value currentIndex += valueSize; } else { unsigned int oLength; Parse(entity.Sub_TLVEntity, 1, buffer + currentIndex, oLength); //解析子嵌套TLV currentIndex += oLength; } currentTLVIndex++; } buffer[currentIndex] = 0; bufferLength = currentIndex; }
然后写测试程序：
// 上发测试数据 unsigned char requestBuf[] = { 0x9F, 0x1C, 0x12, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x30, 0x34, 0x30, 0x34, 0x32, 0x37, 0x31, 0x38, 0x9F, 0x62, 0x01, 0x01, 0x57, 0x12, 0x62, 0x22, 0x89, 0x00, 0x00, 0x02, 0x91, 0x01, 0xD0, 0x90, 0x32, 0x01, 0x02, 0x47, 0x17, 0x13, 0x00, 0x0F, 0x5F, 0x20, 0x0A, 0x48, 0x55, 0x47, 0x55, 0x4F, 0x20, 0x4D, 0x49, 0x4E, 0x47, 0x9F, 0x1F, 0x3C, 0x25, 0x39, 0x39, 0x36, 0x32, 0x32, 0x32, 0x38, 0x39, 0x30, 0x30, 0x30, 0x30, 0x30, 0x32, 0x39, 0x31, 0x30, 0x31, 0x5E, 0x47, 0x55, 0x4F, 0x20, 0x4D, 0x49, 0x4E, 0x47, 0x2F, 0x48, 0x55, 0x5E, 0x30, 0x39, 0x30, 0x33, 0x32, 0x30, 0x31, 0x30, 0x32, 0x34, 0x37, 0x31, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x32, 0x38, 0x39, 0x30, 0x30, 0x3F }; TLVEntity tlvEntity[TLV_MAX_LENGTH]; unsigned int tlv_count; //构造TLV TLVPackage::Construct(requestBuf, sizeof(requestBuf), tlvEntity, tlv_count); unsigned char parseBuf[1024]; unsigned int buf_count; //解析TLV TLVPackage::Parse(tlvEntity, tlv_count, parseBuf, buf_count); if(strncmp((char*)parseBuf, (char*)requestBuf, sizeof(requestBuf)) == 0) { AfxMessageBox("TRUE"); } else { AfxMessageBox("FALSE"); }
最后测试结果中，可以得到最后将弹出“TRUE”的对话框。证明构造TLV得到的TLVEntity，再对这个实体进行解析，可以的到解析后的字节数组，最后通过strncmp的方法比较判断，是否原始字节数组和解析后的字节数组是否一致。
另外，为了方便C#程序员的使用，我对该C++程序重新改写了一下，得出的结果也是一样的。
TLVEntity.cs
///

/// TLV实体 ///

public class TLVEntity { ///

/// 标记 ///

public byte[] Tag { get; set; } ///

/// 数据长度 ///

public byte[] Length { get; set; } ///

/// 数据 ///

public byte[] Value { get; set; } ///

/// 标记占用字节数 ///

public int TagSize { get; set; } ///

/// 数据长度占用字节数 ///

public int LengthSize { get; set; } ///

/// 子嵌套TLV实体 ///

public TLVEntity Sub_TLVEntity { get; set; } }
以及TLVPackage.cs
///

/// TLV打包类 ///

public class TLVPackage { ///

/// 构造TLV ///

///
public static List Construct(byte[] buffer) { List list = new List(); int currentTLVIndex = 0; int currentIndex = 0; int currentStatus = 'T'; //状态字符 int valueSize = 0; TLVEntity tlvEntity = null; while (currentIndex < buffer.Length) { switch (currentStatus) { case 'T': tlvEntity = new TLVEntity(); valueSize = 0; //判断是否单一结构 if ((buffer[currentIndex] & 0x20) != 0x20) { tlvEntity.Sub_TLVEntity = null; //单一结构时将子Tag置空【】 //判断是否多字节Tag if ((buffer[currentIndex] & 0x1f) == 0x1f) { int endTagIndex = currentIndex; while ((buffer[++endTagIndex] & 0x80) == 0x80) ; //判断第二个字节的最高位是否为1 int tagSize = endTagIndex - currentIndex + 1; //计算Tag包含多少字节 tlvEntity.Tag = new byte[tagSize]; Array.Copy(buffer, currentIndex, tlvEntity.Tag, 0, tagSize); tlvEntity.TagSize = tagSize; currentIndex += tagSize; } else { tlvEntity.Tag = new byte[1]; Array.Copy(buffer, currentIndex, tlvEntity.Tag, 0, 1); tlvEntity.TagSize = 1; currentIndex += 1; } } else { //判断是否多字节Tag if ((buffer[currentIndex] & 0x1f) == 0x1f) { int endTagIndex = currentIndex; while ((buffer[++endTagIndex] & 0x80) == 0x80) ; //判断第二个字节的最高位是否为1 int tagSize = endTagIndex - currentIndex + 1; //计算Tag包含多少字节 tlvEntity.Tag = new byte[tagSize]; Array.Copy(buffer, currentIndex, tlvEntity.Tag, 0, tagSize); tlvEntity.TagSize = tagSize; currentIndex += tagSize; } else { tlvEntity.Tag = new byte[1]; Array.Copy(buffer, currentIndex, tlvEntity.Tag, 0, 1); tlvEntity.TagSize = 1; currentIndex += 1; } //分析SubTag int subLength = 0; byte[] temp; if ((buffer[currentIndex] & 0x80) == 0x80) { for (int index = 0; index < 2; index++) { subLength += buffer[currentIndex + 1 + index] << (index * 8); //计算Length域的长度 } temp = new byte[subLength]; Array.Copy(buffer, currentIndex + 3, temp, 0, subLength); } else { subLength = buffer[currentIndex]; temp = new byte[subLength]; Array.Copy(buffer, currentIndex + 1, temp, 0, subLength); } int oLength; tlvEntity.Sub_TLVEntity = new TLVEntity(); List tempList = Construct(temp); tlvEntity.Sub_TLVEntity = tempList[0]; } currentStatus = 'L'; break; case 'L': //判断长度字节的最高位是否为1，如果为1，则该字节为长度扩展字节，由下一个字节开始决定长度 if ((buffer[currentIndex] & 0x80) != 0x80) { tlvEntity.Length = new byte[1]; Array.Copy(buffer, currentIndex, tlvEntity.Length, 0, 1); tlvEntity.LengthSize = 1; valueSize = tlvEntity.Length[0]; currentIndex += 1; } else { //为1的情况 int lengthSize = buffer[currentIndex] & 0x7f; currentIndex += 1; //从下一个字节开始算Length域 for (int index = 0; index < lengthSize; index++) { valueSize += buffer[currentIndex + index] << (index * 8); //计算Length域的长度 } tlvEntity.Length = new byte[lengthSize]; Array.Copy(buffer, currentIndex, tlvEntity.Length, 0, lengthSize); tlvEntity.LengthSize = lengthSize; currentIndex += lengthSize; } currentStatus = 'V'; break; case 'V': tlvEntity.Value = new byte[valueSize]; Array.Copy(buffer, currentIndex, tlvEntity.Value, 0, valueSize); currentIndex += valueSize; //进入下一个TLV构造循环 list.Add(tlvEntity); currentStatus = 'T'; break; default: return new List(); } } return list; } ///

/// 解析TLV ///

///
/// public static byte[] Parse(List list) { byte[] buffer = new byte[4096]; int currentIndex = 0; int currentTLVIndex = 0; int valueSize = 0; while (currentTLVIndex < list.Count()) { valueSize = 0; TLVEntity entity = list[currentTLVIndex]; Array.Copy(entity.Tag, 0, buffer, currentIndex, entity.TagSize); //解析Tag currentIndex += entity.TagSize; for (int index = 0; index < entity.LengthSize; index++) { valueSize += entity.Length[index] << (index * 8); //计算Length域的长度 } if (valueSize > 127) { buffer[currentIndex] = Convert.ToByte(0x80 | entity.LengthSize); currentIndex += 1; } Array.Copy(entity.Length, 0, buffer, currentIndex, entity.LengthSize); //解析Length currentIndex += entity.LengthSize; //判断是否包含子嵌套TLV if (entity.Sub_TLVEntity == null) { Array.Copy(entity.Value, 0, buffer, currentIndex, valueSize); //解析Value currentIndex += valueSize; } else { byte[] tempBuffer = Parse(new List { entity.Sub_TLVEntity }); Array.Copy(tempBuffer, 0, buffer, currentIndex, tempBuffer.Length); //解析子嵌套TLV currentIndex += tempBuffer.Length; } currentTLVIndex++; } byte[] resultBuffer = new byte[currentIndex]; Array.Copy(buffer, 0, resultBuffer, 0, currentIndex); return resultBuffer; } }
接着，写测试程序：
static byte[] requestBuffer = { 0x9F, 0x1C, 0x82, 0x2C, 0x01, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32,0x33, 0x33, 0x30, 0x32, 0x32, 0x37, 0x31, 0x39, 0x36, 0x32, 0x71, 0x07, 0x9f, 0x19, 0x04, 0x11, 0x22, 0x33, 0x44 }; static void Main(string[] args) { Console.WriteLine("待组装的数据包："); requestBuffer.ToList().ForEach(o => { Console.Write("{0},", "0x" + o.ToString("X")); }); Console.WriteLine("\r\n\r\n开始构造TLV"); //构造TLV List list = TLVPackage.Construct(requestBuffer); Console.WriteLine("\r\n构造结束!"); Console.WriteLine("\r\n开始解析TLV"); //解析TLV byte[] responseBuffer = TLVPackage.Parse(list); Console.WriteLine("\r\n解析结束!"); Console.WriteLine("\r\n解析结果："); if (ByteEquals(requestBuffer, responseBuffer)) { Console.WriteLine("Equal!"); } else { Console.WriteLine("Not Equal!"); } Console.ReadKey(); }
运行结果：

总结
TLV在数据通信方面，其实运用得很广泛，在应用层数据通信中，如HTTP协议，HTML，XML语言本身定义了一些标签（Body，Head，Script）对数据串行化，接收方再根据标签解析原始数据，通过浏览器展现出来。因此本质上也是属于TLV协议的设计模式。甚至在传输层的TCP，UDP协议，你完全可以通过TLV实现自定义的应用协议。

Tags:  pboc认证 什么是pboc emvpboc

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