ARPC generation

[deepanshsinghal]

Hi,
Does anyone knows ARPC generation in java card?
Thanks in advance...!!

Deepansh

[UNKNwYSHSA]

1. This is the tool output:

[2017-06-08 10:51:15] BP-Tools - Cryptographic Calculator is ready
********************


[2017-06-08 10:51:17]
EMV Cryptography: ARPC generation finished
****************************************
ARPC Method: 1
Response Code: Y3: Unable to go online (offline approved)
Session key: 7CBA97ABD6CB6E0B29A7457A7332DFC4
Transaction Cryptogram:0C25134A77B0F6B3
----------------------------------------
ARPC generated: 47CA7F6274A9FCB1

2. And we calculate ARPC using method1, EMV specification shows the details:

8.2.1 ARPC Method 1
ARPC Method 1 for the generation of an 8-byte ARPC consists of applying the
Triple-DES algorithm as specified in Annex B1.1 to:
the 8-byte ARQC generated by the ICC as described in section 8.1
the 2-byte Authorisation Response Code (ARC)
using the 16-byte Application Cryptogram Session Key SKAC (see section 8.1) in
the following way:
1. Pad the 2-byte ARC with six zero bytes to obtain the 8-byte number
X := (ARC || '00'|| '00' || '00' || '00' || '00' || '00')
2. Compute Y: = ARQC ^ X.
3. The 8-byte ARPC is then obtained by
ARPC := DES3(SKAC)[Y]

3. Calculate ARPC manually.
[INPUT] Session key: 7CBA97ABD6CB6E0B29A7457A7332DFC4
[INPUT] ARQC: 0C25134A77B0F6B3
[ARC PADDED] ARC: "Y3" => 5933 + 000000000000
[XOR] ARQC ^ ARC => 5516134A77B0F6B3
[OUTPUT] Encrypt with algorithm 3DES, result: 47CA7F6274A9FCB1
[RESULT] Same as the tool's result.

4 Source code to calculate ARPC with JavaCard:

Code: Select all

      switch (buf[ISO7816.OFFSET_INS])
      {
      case (byte) 0x00:
         apdu.setIncomingAndReceive();
         key.setKey(buf, ISO7816.OFFSET_CDATA);
         break;
      case (byte) 0x02:
         short dataLen2 = apdu.setIncomingAndReceive();
         // Note: Receive more data bytes if exists with apdu.receiveBytes().
         Cipher cipher = Cipher.getInstance(Cipher.ALG_DES_ECB_NOPAD, false);
         cipher.init(key, Cipher.MODE_ENCRYPT);
         short resultLen2 = cipher.doFinal(buf, ISO7816.OFFSET_CDATA, dataLen2, buf, (short) 0);
         apdu.setOutgoingAndSend((short) 0, resultLen2);
         JCSystem.requestObjectDeletion();
         break;
      default:
         ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
      }

5. APDU command:

>> /select 112233445500
>> 00 A4 04 00 06 11 22 33 44 55 00 00
<< 90 00

>> /send 00000000107CBA97ABD6CB6E0B29A7457A7332DFC4
>> 00 00 00 00 10 7C BA 97 AB D6 CB 6E 0B 29 A7 45 7A 73 32 DF C4
<< 90 00

>> /send 00020000085516134A77B0F6B3
>> 00 02 00 00 08 55 16 13 4A 77 B0 F6 B3
<< 47 CA 7F 62 74 A9 FC B1 90 00

[deepanshsinghal]

Thanks a lot You just saved my vacations.
You are the best.

Let me implement that

[deepanshsinghal]

Code: Select all

public void generateSecondAC(APDU apdu, byte[] apduBuffer) {
      short dataLen = apduBuffer[OFFSET_LC];
      Util.arrayCopy(apduBuffer, (short) 5, onlineARPC, (short) 0, (short) 8);
      
      Util.arrayCopy(apduBuffer, (short) 0x0D, responseCode, (short) 0, (short) 2);
         
      byte[] Y = new byte[8];
      // XOR between ARQC and Response Code as per mentioned in ARPC method 1 EMV book 2 (8.2.1)
      Y = xor(chipMAC, responseCode);
      
      Cipher cipher = Cipher.getInstance(Cipher.ALG_DES_ECB_NOPAD, false);
        cipher.init(theCrypto.sk, Cipher.MODE_ENCRYPT);
      
      short resultLen = cipher.doFinal(Y, (short) 0, (short) (8), apduBuffer, (short) (dataLen + 10));
      
      apdu.setOutgoingAndSend((short) (dataLen + 10), (short) (resultLen));
      JCSystem.requestObjectDeletion();
   }
   
   private static byte[] padding(byte[] data) {
      // int dataLen = data.length;
      // int paddingSize = (8 - (dataLen + 1) % 8);
      // return fillRight(data, (byte) 0x00, paddingSize);

      byte[] t = new byte[ (short) (data.length - data.length % 8 + 8)];
      Util.arrayCopy(data, (short) 0, t, (short) 0, (short) data.length);
      for (short i = (short) data.length; i < t.length; i++)
         t[i] = (byte) (i == data.length ? 0x00 : 0x00);
      data = t;
      return data;

   }

can you check what i am missing?

[UNKNwYSHSA]

Code: Select all

public void generateSecondAC(APDU apdu, byte[] apduBuffer) {
      short dataLen = apduBuffer[OFFSET_LC];
      Util.arrayCopy(apduBuffer, (short) 5, onlineARPC, (short) 0, (short) 8);
      
      Util.arrayCopy(apduBuffer, (short) 0x0D, responseCode, (short) 0, (short) 2);
         
      byte[] Y = new byte[8];
      // XOR between ARQC and Response Code as per mentioned in ARPC method 1 EMV book 2 (8.2.1)
      Y = xor(chipMAC, responseCode);
      
      Cipher cipher = Cipher.getInstance(Cipher.ALG_DES_ECB_NOPAD, false);
        cipher.init(theCrypto.sk, Cipher.MODE_ENCRYPT);
      
      short resultLen = cipher.doFinal(Y, (short) 0, (short) (8), apduBuffer, (short) (dataLen + 10));
      
      apdu.setOutgoingAndSend((short) (dataLen + 10), (short) (resultLen));
      JCSystem.requestObjectDeletion();
   }
   
   private static byte[] padding(byte[] data) {
      // int dataLen = data.length;
      // int paddingSize = (8 - (dataLen + 1) % 8);
      // return fillRight(data, (byte) 0x00, paddingSize);

      byte[] t = new byte[ (short) (data.length - data.length % 8 + 8)];
      Util.arrayCopy(data, (short) 0, t, (short) 0, (short) data.length);
      for (short i = (short) data.length; i < t.length; i++)
         t[i] = (byte) (i == data.length ? 0x00 : 0x00);
      data = t;
      return data;

   }

can you check what i am missing?

Let me have a look.

[UNKNwYSHSA]

Code: Select all

public void generateSecondAC(APDU apdu, byte[] apduBuffer) {
      short dataLen = apduBuffer[OFFSET_LC];
      Util.arrayCopy(apduBuffer, (short) 5, onlineARPC, (short) 0, (short) 8);
      
      Util.arrayCopy(apduBuffer, (short) 0x0D, responseCode, (short) 0, (short) 2);
         
      byte[] Y = new byte[8];
      // XOR between ARQC and Response Code as per mentioned in ARPC method 1 EMV book 2 (8.2.1)
      Y = xor(chipMAC, responseCode);
      
      Cipher cipher = Cipher.getInstance(Cipher.ALG_DES_ECB_NOPAD, false);
        cipher.init(theCrypto.sk, Cipher.MODE_ENCRYPT);
      
      short resultLen = cipher.doFinal(Y, (short) 0, (short) (8), apduBuffer, (short) (dataLen + 10));
      
      apdu.setOutgoingAndSend((short) (dataLen + 10), (short) (resultLen));
      JCSystem.requestObjectDeletion();
   }
   
   private static byte[] padding(byte[] data) {
      // int dataLen = data.length;
      // int paddingSize = (8 - (dataLen + 1) % 8);
      // return fillRight(data, (byte) 0x00, paddingSize);

      byte[] t = new byte[ (short) (data.length - data.length % 8 + 8)];
      Util.arrayCopy(data, (short) 0, t, (short) 0, (short) data.length);
      for (short i = (short) data.length; i < t.length; i++)
         t[i] = (byte) (i == data.length ? 0x00 : 0x00);
      data = t;
      return data;

   }

can you check what i am missing?

Can you give me the APDU you sent?

[deepanshsinghal]

Can you give me the APDU you sent?

Code: Select all

>> /select A0000000494F434C435051
>> 00 A4 04 00 0B A0 00 00 00 49 4F 43 4C 43 50 51 00
<< 90 00

>> /send 80AE40002B00000000031400000000000003560420008000035616080200549E74AD22000000000000000000003F0002
>> 80 AE 40 00 2B 00 00 00 00 03 14 00 00 00 00 00 00 03 56 04 20 00 80 00 03 56 16 08 02 00 54 9E 74 AD 22 00 00 00 00 00 00 00 00 00 00 3F 00 02 00
<< 2B BA 1E CD 05 17 85 5A 90 00

>> /send 80AE20000A980B4B43FF9B9F510000
>> 80 AE 20 00 0A 98 0B 4B 43 FF 9B 9F 51 00 00
<< 2D AD 26 F6 0A 7D A8 66 90 00

Here
master key: 01010101010101010101010101010101020

>> /send 80AE20000A980B4B43FF9B9F510000
in this "980B4B43FF9B9F51" is ARPC from BP-Tool
0000 is custom response code

[UNKNwYSHSA]

1 Following your code:

Code: Select all

Y = xor(chipMAC, responseCode);

What is the chipMAC?
2 The response code is 2 bytes, it is hex value from "00" to "Z3", it can not be 0000. Hex value of "00" is 3030.

[deepanshsinghal]

1 Following your code:

Code: Select all

Y = xor(chipMAC, responseCode);

What is the chipMAC?
2 The response code is 2 bytes, it is hex value from "00" to "Z3", it can not be 0000. Hex value of "00" is 3030.

Chipmac is ARQC that is generating earlier

[UNKNwYSHSA]

1 Following your code:

Code: Select all

Y = xor(chipMAC, responseCode);

What is the chipMAC?
2 The response code is 2 bytes, it is hex value from "00" to "Z3", it can not be 0000. Hex value of "00" is 3030.

Chipmac is ARQC that is generating earlier

OK, Replace Response Code to 3030 and calculate again. What about the result?