Hashing trouble

Question

Hi, I've been given an issue to solve but I'm not getting close to the solution.
Problem is to hash (MD5 128 bits) an ip address (with salt = 0x12345678) following this example.
"+The IP is represented as 4 bytes thus: 217.57.160.193 = in Hex D9.39.A0.C1, so the 32-bit value of the IP is 0xD939A0C1.+
+When hashing the IP, the binary buffer sent for the MD5 operation is always 8 bytes long, in which the first 4 bytes are the salt and the last 4 bytes are the IP value+".
In this case, the binary buffer sent to the MD5 is: 0x12345678D939A0C1.
Result should be: 6cb3fa0c1e04fc9d9f37a2617fa57bb4.
I addressed the first part with this code:
long salt = (long) 0x12345678;
String ipAddress = "217.57.160.193";
String strToHash;
byte[] hsh = null;
long result = 0;
String[] octets = ipAddress.split("\\.");
+for (int i = 3; i >= 0; i--) {+
result |= (Long.parseLong(octets[3 - i]) << (i * 8));
+}+
result = result & 0xFFFFFFFF;
System.out.println("217.57.160.193 in hex = " Long.toHexString(result));+
Obtaining: 0xD939A0C1
Then I tried to hash w/ salt:
String md5="";
byte[] md5Byte = null;
+try {+
+//md5Byte = DigestUtils.md5(((Long.toHexString(salt)) + (Long.toHexString(result))).getBytes("UTF-8"));+
md5 = DigestUtils.md5Hex(strToHash.getBytes());
+} catch (Exception ex) {+
java.util.logging.Logger.getLogger(HttpMonitorNG.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
+}+
System.out.println("217.57.160.193 hashed = " md5);+
Obtaining this value: 0b348be5b3ebe7c54bff9170a24a5362
Any idea would be appreciated.
Thank you
ny

Answer 1

There is just so so so much wrong with that code.
This gives the result you expect -
final byte[] salt =
            (byte) 0x12, (byte) 0x34, (byte) 0x56, (byte) 0x78
        final byte[] ip =
            (byte) 0xD9, (byte) 0x39, (byte) 0xA0, (byte) 0xC1
        final MessageDigest digestAgent = MessageDigest.getInstance("MD5");
        digestAgent.update(salt);
        digestAgent.update(ip);
        final byte[] digest = digestAgent.digest();
        for (byte b : digest)
            System.out.printf("%02x", b & 0xff);
        System.out.println();and using your original salt and IP data types            int salt = 0x12345678;
            String ipAddress = "217.57.160.193";
            final MessageDigest digestAgent = MessageDigest.getInstance("MD5");
            for (int j = 24; j >= 0; j -= 8)
                digestAgent.update((byte) (salt >>> j));
            for (String s : ipAddress.split("\\."))
                digestAgent.update((byte) Integer.parseInt(s));
            final byte[] digest = digestAgent.digest();
            for (byte b : digest)
                System.out.printf("%02x", b & 0xff);
           System.out.println();Edited by: sabre150 on Jul 31, 2009 1:00 PM
Refined second bit of code