讀寫MifareClassic協議的NFC卡

轉自：http://www.cnblogs.com/haoxinyue/archive/2012/05/03/2479599.html

先了解一下MifareClassic協議

在android sdk 的文檔中，描述道 “all MifareClassic I/O operations will be supported, andMIFARE_CLASSIC NDEF tags will also be supported. In either case,NfcA will also be enumerated on the tag, because all MIFARE Classic tags are alsoNfcA.” 所以說NFCA協議是兼容MifareClassic 協議的， 我們可以通過NfcA在android的相關類來處理給予MifareClassic 的RFID卡。

一般來說，給予MifareClassic的射頻卡，一般內存大小有3種：

1K: 16個分區(sector)，每個分區4個塊(block)，每個塊(block) 16個byte數據

2K: 32個分區，每個分區4個塊(block)，每個塊(block) 16個byte數據

4K：64個分區，每個分區4個塊(block)，每個塊(block) 16個byte數據

對於所有基於MifareClassic的卡來說，每個區最後一個塊叫Trailer，16個byte， 主要來存放讀寫該區的key，可以有A，B兩個KEY，每個key長6byte，默認的key一般是FF 或 0，最後一個塊的內存結構如下：

Block 0 Data 16bytes

Block 1 Data 16 bytes

Block 2 Data 16 bytes

Block 3 Trailer 16 bytes

Trailer:

Key A: 6 bytes

Access Conditions: 4 bytes

Key B: 6 bytes

所以在寫卡的內存的時候，一般不能寫每個sector的最後一個block，除非你有要修改KEY和訪問權限的需求。如果KEY A 被你不小心修改掉了，而你不知道修改成什麼，那與之對應的那個sector你就沒有辦法訪問了。因爲在MifareClassic中，如果你要讀取數據，那麼必須要有這個數據地址所在的sector的權限，這個權限就是這個sector的trailer的keyA或KEY B。

讀數據的例子：

//tag 就是在上一篇中onNewIntent中獲取的tag

MifareClassic mc = MifareClassic.get(tag);
        short startAddress = 0;
        short endAddress = 5;

        byte[] data = new byte[(endAddress - startAddress + 1 ) * ByteCountPerBlock];
        
        try {            
            mc.connect();for (short i = startAddress; i <= endAddress; i++ ,time++) {
                boolean auth = false;
                short sectorAddress = getSectorAddress(i);
                auth = mc.authenticateSectorWithKeyA(sectorAddress, MifareClassic.KEY_DEFAULT);
                if (auth){
                    
                    //the last block of the sector is used for KeyA and KeyB cannot be overwritted
                    short readAddress = (short)(sectorAddress == 0 ? i : i + sectorAddress);
                    
                    byte[] response = mc.readBlock(readAddress);
                    CombineByteArray(data, response, time * ByteCountPerBlock);
                }
                else{
                    throw new NfcException(NfcErrorCode.TemporaryError,
                            "Authorization Error.");
                }
            }

            mc.close();
            
        }
        catch (NfcException ne) {
            throw ne;
        }
        catch (IOException e) {
            throw new NfcException(NfcErrorCode.TemporaryError,
                    "Get response, what it is not successfully.", e);
        }
        finally
        {
            try {
                mc.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

寫數據的例子：

//tag 就是在上一篇中onNewIntent中獲取的tag
MifareClassic mc = MifareClassic.get(tag);

            try {
                mc.connect();
                boolean auth = false;
                short sectorAddress = 0
                auth = mc.authenticateSectorWithKeyA(sectorAddress,
                        MifareClassic.KEY_DEFAULT);
                if (auth) {
                    //the last block of the sector is used for KeyA and KeyB cannot be overwritted
                    
                    mc.writeBlock(readAddress, dataTemp);

                    mc.close();
                } 
            }finally
            {
                try {
                    mc.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }