3DES

[deepanshsinghal]

I tried with openemv implementation also... but no success

Can you tell me, how do you verify the result? And i will have a try to resolve this problem. I have no terminate application to verify the applet functions.

There is BP-Tool you can use that to verify
Check out this link " https://eftlab.co.uk/index.php/downloads/bp-tools " you'll get that Tool

[UNKNwYSHSA]

OK, let me hava a try.

[deepanshsinghal]

OK, let me hava a try.

Thanks, any help from you is appreciated

[UNKNwYSHSA]

[UNKNwYSHSA]

Which version of EMV specification are you watching?
The session key can be calculated and same as the tool's result.
But the AC, ..., always different!

[deepanshsinghal]

Which version of EMV specification are you watching?
The session key can be calculated and same as the tool's result.
But the AC, ..., always different!

EMV 4.3 Book 2 Security and Key Management (8.1.1) as per you suggested with that i am generating AC with BP-Tool and i have one java program which calculate compute AC.. .... Both results are same.

[UNKNwYSHSA]

You need to see Version 4.2. Not 4.3. Can you send your java programe to me? The java programe can be decompiled and we can know how it works.

[deepanshsinghal]

You need to see Version 4.2. Not 4.3. Can you send your java programe to me? The java programe can be decompiled and we can know how it works.

But the concept to generate the AC will be the same no matter it is 4.2 or 4.3

Code: Select all

   public static byte[] computeMAC(byte[] key, byte[] plaintext) {

      System.out.println("MAC : key " + Arrays.toString(key));
      System.out.println("MAC : plaintext " + Arrays.toString(plaintext));
      byte[] ka = new byte[8];
      System.arraycopy(key, 0, ka, 0, 8);
      byte[] kb = new byte[8];

      System.arraycopy(key, 8, kb, 0, 8);

      SecretKey skeya = new SecretKeySpec(ka, "DES");
      SecretKey skeyb = new SecretKeySpec(kb, "DES");
      byte[] current = new byte[8];
      byte[] mac = new byte[] { (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0 };

      System.out.println("KEY " + Utils.toHexString(key));
      System.out.println("DATA " + Utils.toHexString(plaintext));
      plaintext = padding(plaintext);
      System.out.println("AP DATA " + Utils.toHexString(plaintext));
      Cipher des;
      try {
         for (int i = 0; i < plaintext.length; i += 8) {
            System.out.println("8 BYTES " + current);
            System.arraycopy(plaintext, i, current, 0, 8);
            mac = xor(current, mac);
            des = Cipher.getInstance("DES/CBC/NoPadding");
            des.init(Cipher.ENCRYPT_MODE, skeya, new IvParameterSpec(new byte[8]));
            mac = des.doFinal(mac);
         }
         des = Cipher.getInstance("DES/CBC/NoPadding");
         des.init(Cipher.DECRYPT_MODE, skeyb, new IvParameterSpec(new byte[8]));
         mac = des.doFinal(mac);

         des.init(Cipher.ENCRYPT_MODE, skeya, new IvParameterSpec(new byte[8]));
         mac = des.doFinal(mac);
      } catch (Exception e) {
         e.printStackTrace();
      }
      return mac;
   }

[UNKNwYSHSA]

You need to see Version 4.2. Not 4.3. Can you send your java programe to me? The java programe can be decompiled and we can know how it works.

But the concept to generate the AC will be the same no matter it is 4.2 or 4.3

Code: Select all

   public static byte[] computeMAC(byte[] key, byte[] plaintext) {

      System.out.println("MAC : key " + Arrays.toString(key));
      System.out.println("MAC : plaintext " + Arrays.toString(plaintext));
      byte[] ka = new byte[8];
      System.arraycopy(key, 0, ka, 0, 8);
      byte[] kb = new byte[8];

      System.arraycopy(key, 8, kb, 0, 8);

      SecretKey skeya = new SecretKeySpec(ka, "DES");
      SecretKey skeyb = new SecretKeySpec(kb, "DES");
      byte[] current = new byte[8];
      byte[] mac = new byte[] { (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0 };

      System.out.println("KEY " + Utils.toHexString(key));
      System.out.println("DATA " + Utils.toHexString(plaintext));
      plaintext = padding(plaintext);
      System.out.println("AP DATA " + Utils.toHexString(plaintext));
      Cipher des;
      try {
         for (int i = 0; i < plaintext.length; i += 8) {
            System.out.println("8 BYTES " + current);
            System.arraycopy(plaintext, i, current, 0, 8);
            mac = xor(current, mac);
            des = Cipher.getInstance("DES/CBC/NoPadding");
            des.init(Cipher.ENCRYPT_MODE, skeya, new IvParameterSpec(new byte[8]));
            mac = des.doFinal(mac);
         }
         des = Cipher.getInstance("DES/CBC/NoPadding");
         des.init(Cipher.DECRYPT_MODE, skeyb, new IvParameterSpec(new byte[8]));
         mac = des.doFinal(mac);

         des.init(Cipher.ENCRYPT_MODE, skeya, new IvParameterSpec(new byte[8]));
         mac = des.doFinal(mac);
      } catch (Exception e) {
         e.printStackTrace();
      }
      return mac;
   }

Waiting your java programme.

[UNKNwYSHSA]

I got that!!!

Steps:
1 Encrypt data blocks using first des key with cbc mode;
2 Decrypt the result with second des key;
3 Encrypt the result of step 2 with first des key;
The AC calculated.

Example:
Session key: 7CBA97ABD6CB6E0B 29A7457A7332DFC4
Fist des key: 7CBA97ABD6CB6E0B
Second des key: 29A7457A7332DFC4
Data: Terminal Data + ICC Data + 800000(Pad)
Data: 0000000010000000000000000710000000000007101302050030901B6A + 3C00005503A4A082 + 800000

Calculate:
1Key: 7CBA97ABD6CB6E0B
IV: 0000000000000000
m: 0000000010000000000000000710000000000007101302050030901B6A3C00005503A4A082800000
s: AB45C4A8204CA392374F2F5FCAE5A8A2E18B65F7554966C5E3697C946CD8B284EFC6ECB7A354B1CA
2 Key: 29A7457A7332DFC4
IV: 0000000000000000
m: EFC6ECB7A354B1CA
s: 388B6AA70A89AB7C
3 Key: 7CBA97ABD6CB6E0B
IV: 0000000000000000
m: 388B6AA70A89AB7C
s: 50C221AF54C1706A
The result is: 50C221AF54C1706A

Same as the tool calculated.

Session key: 7CBA97ABD6CB6E0B29A7457A7332DFC4
Terminal data: 0000000010000000000000000710000000000007101302050030901B6A
ICC data: 3C00005503A4A082
Padding method: Method 2 (EMV spec or e.g. VISA CV14)
----------------------------------------
AC generated: 50C221AF54C1706A

Note:
The implementation of this algorithm in javacard is: Signature.ALG_DES_MAC8_ISO9797_1_M2_ALG3