At first glance, I have the same problem as many. But my case a bit more complex.
Preconditions:
Project language: Java 11
Network Server: Orbiwise NS (https://eu.saas.orbiwise.com/)
Device: (STM32 + Wifi module) connection via Lorawan gateway to Orbiwise and using TCP socket via wifi.
Input data:
From TCP socket received byte array:
40 24 fa fa 01 c2 c5 25 03 06 01 43 a4 99 5a c1
85 71 0c 87 38 84 53 9a 80 6c 5a 14 da f8 ff 7c
21 83 8f 78 8e ec f2 7d 4e 4e 07
(43 bytes)
On Orbiwise have corresponding to it uplink payload:
31 19 10 07 01 13 51 25 09 01 00 00 00 00 33 04
00 00 5A 00 00 00 EB 0D 00 00 64 EB
(28 bytes)
Task:
Decrypt data from TCP socket to have decrypted payload in the same format as on Orbiwise
Approaches were used without positive result:
- https://github.com/jsubercaze/javalora
- https://github.com/huahang/crypto-utils/blob/master/crypto-utils/src/main/java/im/chic/utils/crypto/AesUtils.java
- https://github.com/matthiaszimmermann/ttn_decoder_java - core code for mine.
All project above was written a long time ago and not helped me. This one helped, but written on Node JS: https://github.com/anthonykirby/lora-packet
From LoraWan specification I got that used "AES/ECB/NoPadding" method and my current code looks like:
package org.thethingsnetwork.main.java.org.thethingsnetwork.util.security;
import java.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
public class Crypto {
/**
* Decrypts TTN data_raw payload to data according to the TTN REST API.
* @param pld encrypted message payload from ttn mqtt message
* @param K the TTN application key
* @param IV
* @return decrypted payload
* @throws Exception
*/
public static byte[] decrypt(byte [] pld, byte [] K, byte [] IV) throws Exception {
byte [] devAddr = getDevAddr(pld);
byte [] frameCounter = getFrameCounter(pld);
byte [] result = initializeResult(pld);
byte [] Ai = new byte[16];
byte [] Si = null;
for(int i = 0; i < result.length; i += 16) {
int blockSeqCnt = (i >> 4) + 1;
computeAi(Ai, devAddr, frameCounter, blockSeqCnt);
Si = encryptAES(Ai, K, IV);
for(int j=0; j < 16 && i+j < result.length; j++) {
result[i+j] ^= Si[j];
}
}
return result;
}
/**
* Converts TTN payload data to data_plain according to the TTN REST API.
* Decode a text using base 64 decoding.
* @param decryptedText
* @return
*/
public static String toPlainText(String decryptedText) {
byte [] data = Base64.getDecoder().decode(decryptedText);
StringBuffer plain = new StringBuffer();
for(int i = 0; i < data.length; i++) {
plain.append((char)data[i]);
}
return plain.toString();
}
public static byte [] getDevAddr(byte [] payload) {
byte [] devAddr = new byte[4];
System.arraycopy(payload, 1, devAddr, 0, 4);
return devAddr;
}
public static byte [] getFrameCounter(byte [] payload) {
byte [] frameCounter = new byte[2];
System.arraycopy(payload, 6, frameCounter, 0, 2);
return frameCounter;
}
public static byte [] initializeResult(byte [] payload) {
byte [] result = new byte[payload.length - 13];
for(int i = 0; i < result.length; i++) {
result[i] = payload[i+9];
}
return result;
}
public static void computeAi(byte [] a, byte [] devAddr, byte [] frameCounter, int blockSeqCnt) {
a[0] = 0x01;
a[1] = 0x00;
a[2] = 0x00;
a[3] = 0x00;
a[4] = 0x00;
a[5] = 0; // 0 for uplink frames 1 for downlink frames;
a[6] = devAddr[0]; // LSB devAddr 4 bytes
a[7] = devAddr[1]; // ..
a[8] = devAddr[2]; // ..
a[9] = devAddr[3]; // MSB
a[10] = frameCounter[0]; // LSB framecounter
a[11] = frameCounter[1]; // MSB framecounter
a[12] = 0x00; // Frame counter upper Bytes
a[13] = 0x00;
a[14] = 0x00;
a[15] = (byte)blockSeqCnt; // block sequence counter 1,2,3...
}
/**
* AES encrpytion.
*/
public static byte[] encryptAES(byte [] data, byte [] key, byte [] iv) throws Exception {
Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding", "SunJCE");
SecretKeySpec keySpec = new SecretKeySpec(key, "AES");
cipher.init(Cipher.DECRYPT_MODE, keySpec);
return cipher.doFinal(data);
}
}
And second class - test:
package org.thethingsnetwork.util.security;
import org.apache.commons.codec.DecoderException;
import org.junit.Assert;
import org.junit.Test;
import org.thethingsnetwork.main.java.org.thethingsnetwork.util.security.Crypto;
import org.apache.commons.codec.binary.Hex;
public class CryptoTest {
private byte [] SEMTECH_DEFAULT_KEY = Hex.decodeHex("2E12E8BD30FE2FB2D8DE609747D2569F".toCharArray());
public static final byte [] IV = new byte [] {
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0
}; // initialization vector – IV
// example data from a ttn message
public static final byte[] TEXT_RAW = new byte[] {0x40, 0x24, (byte) 0xfa, (byte) 0xfa, 0x01, (byte) 0xc2,
(byte) 0xc5, 0x25, 0x03, 0x06, 0x01, 0x43, (byte) 0xa4, (byte) 0x99, 0x5a, (byte) 0xc1, (byte) 0x85, 0x71,
0x0c, (byte) 0x87, 0x38, (byte) 0x84, 0x53, (byte) 0x9a, (byte) 0x80, 0x6c, 0x5a, 0x14, (byte) 0xda,
(byte) 0xf8, (byte) 0xff, 0x7c, 0x21, (byte) 0x83, (byte) 0x8f, 0x78, (byte) 0x8e, (byte) 0xec, (byte) 0xf2,
0x7d, 0x4e, 0x4e, 0x07};
public CryptoTest() throws DecoderException {
}
@Test
public void testDecoder() throws Exception {
byte[] decryptedText = Crypto.decrypt(TEXT_RAW, SEMTECH_DEFAULT_KEY, IV);
printTheByteToString(decryptedText);
}
/**
* Method for prin in command line byte array. For debug necessary
* @param b - input byte array
*/
private void printTheByteToString (byte[] b) {
for (byte val : b) {
System.out.print(String.format("%02x ", val));
}
}
}
I've checked the code a hundred times but no positive result - the decrypted message is different from on Orbiwise.
I've checked the data using NodeJs project (https://github.com/anthonykirby/lora-packet) and all is correct. But can't resolve the task using my Java code.
Can some body help me in this situation? Thanks a lot in advance!
