Decoding LoRaWAN Packet
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The document discusses decoding a LoRaWAN packet received at a gateway. It provides steps to: 1) Use an online tool to decode the base64 encoded packet and obtain the PHYPayload 2) Use a Python script along with the PHYPayload, dev address, and key to decrypt the payload and obtain a string of decimal values 3) Convert the decimal values to hexadecimal to reveal the original message of "hello world".
![Decodingof LoRaWAN packets
The above screenshotisthe received LoRaWAN packetatthe gatewaywhichneedstobe decoded
to understandif the correctdata are beingsenttoTTN.
From the LoRaWAN packetdata (QNIfASaABAABA/uB+N3FPLnND5ufMW6z) whichis inbase 64
encodedformatisdecodedusing step(1) toobtain FRMpayload.
1. https://LoRaWAN-packet-decoder-0ta6puiniaut.runkit.sh
Thisweblinkhelpsdecodingthe base 64 data receivedatthe gateway
Assumingbase64-encoded packet
QNIfASaABAABA/uB+N3FPLnND5ufMW6z
Message Type = Data
PHYPayload = 40D21F01268004000103FB81F8DDC53CB9CD0F9B9F316EB3
( PHYPayload = MHDR[1] | MACPayload[..] | MIC[4] )
MHDR = 40
MACPayload = D21F01268004000103FB81F8DDC53CB9CD0F9B
MIC = 9F316EB3
( MACPayload = FHDR | FPort | FRMPayload )
FHDR = D21F0126800400
FPort = 01
FRMPayload = 03FB81F8DDC53CB9CD0F9B
( FHDR = DevAddr[4] | FCtrl[1] | FCnt[2] | FOpts[0..15] )
DevAddr = 26011FD2 (Big Endian)
FCtrl = 80
FCnt = 0004 (BigEndian)
FOpts =](https://image.slidesharecdn.com/decodingoflorawanpackets-190420152528/85/Decoding-LoRaWAN-Packet-1-320.jpg)
![Copythe FRMpayloadfrom (1) to payload, fcntto sequence_counter,andenterthe dev_addrand
Appskeyusedtoencryptthe payload.
Pressctrl+x -> y -> ENTER to save the pythonscript.
To run the script type “python payload_decrypt.py”andhitenter.
Upon executionof the payload_decrypt.pyastringof decimal valuesisobtained;thisstringisthen
decodedusingdecimal tohex converterusingonline tool.
The cryptologylibraryhasdependencyon setuptools andpythonversioninLinux andRaspbian,
whichtakesa quite a biteffort.However,ImigratedtoAnacondaIDEin windowstoexecute the
pythondecryptscript.
Assumingbase64-encoded packet
QIsbASaABQABlKmBif/36J2UWcXZ/hdK
Message Type = Data
PHYPayload = 408B1B01268005000194A98189FFF7E89D9459C5D9FE174A
( PHYPayload = MHDR[1] | MACPayload[..] | MIC[4] )
MHDR = 40](https://image.slidesharecdn.com/decodingoflorawanpackets-190420152528/85/Decoding-LoRaWAN-Packet-3-320.jpg)
![MACPayload = 8B1B01268005000194A98189FFF7E89D9459C5
MIC = D9FE174A
( MACPayload = FHDR | FPort | FRMPayload )
FHDR = 8B1B0126800500
FPort = 01
FRMPayload = 94A98189FFF7E89D9459C5
( FHDR = DevAddr[4] | FCtrl[1] | FCnt[2] | FOpts[0..15] )
DevAddr = 26011B8B(Big Endian)
FCtrl = 80
FCnt = 0005 (BigEndian)
FOpts =
Message Type = Unconfirmed Data Up
Direction = up
FCnt = 5
FCtrl.ACK = false
FCtrl.ADR = true](https://image.slidesharecdn.com/decodingoflorawanpackets-190420152528/85/Decoding-LoRaWAN-Packet-4-320.jpg)
![from lora.crypto import loramac_decrypt
payload = '94A98189FFF7E89D9459C5'
sequence_counter = 5
key = 'DF2FE61E548EF67A186ECFF15E2A09AB'
dev_addr = '26011B8B'
print(loramac_decrypt(payload, sequence_counter, key, dev_addr))
Resultobtainedbyexecutingthe payload_decrypt.py
[104, 101,108, 108, 111,32, 119, 111,114, 108, 100]
To convertthisbase 64 valuesto ASCIIValue,letususesanonline converter
https://www.branah.com/ascii-converter](https://image.slidesharecdn.com/decodingoflorawanpackets-190420152528/85/Decoding-LoRaWAN-Packet-5-320.jpg)
Decoding LoRaWAN Packet
- 1. Decodingof LoRaWAN packets The above screenshotisthe received LoRaWAN packetatthe gatewaywhichneedstobe decoded to understandif the correctdata are beingsenttoTTN. From the LoRaWAN packetdata (QNIfASaABAABA/uB+N3FPLnND5ufMW6z) whichis inbase 64 encodedformatisdecodedusing step(1) toobtain FRMpayload. 1. https://LoRaWAN-packet-decoder-0ta6puiniaut.runkit.sh Thisweblinkhelpsdecodingthe base 64 data receivedatthe gateway Assumingbase64-encoded packet QNIfASaABAABA/uB+N3FPLnND5ufMW6z Message Type = Data PHYPayload = 40D21F01268004000103FB81F8DDC53CB9CD0F9B9F316EB3 ( PHYPayload = MHDR[1] | MACPayload[..] | MIC[4] ) MHDR = 40 MACPayload = D21F01268004000103FB81F8DDC53CB9CD0F9B MIC = 9F316EB3 ( MACPayload = FHDR | FPort | FRMPayload ) FHDR = D21F0126800400 FPort = 01 FRMPayload = 03FB81F8DDC53CB9CD0F9B ( FHDR = DevAddr[4] | FCtrl[1] | FCnt[2] | FOpts[0..15] ) DevAddr = 26011FD2 (Big Endian) FCtrl = 80 FCnt = 0004 (BigEndian) FOpts =
- 2. Message Type = Unconfirmed Data Up Direction = up FCnt = 4 FCtrl.ACK = false FCtrl.ADR = true Download LoRaWAN packetdecoder https://github.com/jieter/python-lora https://github.com/jieter/python-lora/tree/master/tests Thisscript hasdependencyoncryptography.cryptographyrequires cffi whichinturnrequires libffi- dev,python-devand openssl. $sudo apt-get install libffi-dev $sudo apt-get install python-dev $sudo apt-get install python3-dev $sudo apt-get install openssl $pip install python-lora The FRMpayloadis thenusedinpayload_decrypt.pyalongwithsequencecounter(fcnt),dev_addrof the node and Appskey toobtainthe decimal equivalentof the payload. $ mkdir lora_decrypt $ cd lora_decrypt $ sudo nano payload_decrypt.py
- 3. Copythe FRMpayloadfrom (1) to payload, fcntto sequence_counter,andenterthe dev_addrand Appskeyusedtoencryptthe payload. Pressctrl+x -> y -> ENTER to save the pythonscript. To run the script type “python payload_decrypt.py”andhitenter. Upon executionof the payload_decrypt.pyastringof decimal valuesisobtained;thisstringisthen decodedusingdecimal tohex converterusingonline tool. The cryptologylibraryhasdependencyon setuptools andpythonversioninLinux andRaspbian, whichtakesa quite a biteffort.However,ImigratedtoAnacondaIDEin windowstoexecute the pythondecryptscript. Assumingbase64-encoded packet QIsbASaABQABlKmBif/36J2UWcXZ/hdK Message Type = Data PHYPayload = 408B1B01268005000194A98189FFF7E89D9459C5D9FE174A ( PHYPayload = MHDR[1] | MACPayload[..] | MIC[4] ) MHDR = 40
- 4. MACPayload = 8B1B01268005000194A98189FFF7E89D9459C5 MIC = D9FE174A ( MACPayload = FHDR | FPort | FRMPayload ) FHDR = 8B1B0126800500 FPort = 01 FRMPayload = 94A98189FFF7E89D9459C5 ( FHDR = DevAddr[4] | FCtrl[1] | FCnt[2] | FOpts[0..15] ) DevAddr = 26011B8B(Big Endian) FCtrl = 80 FCnt = 0005 (BigEndian) FOpts = Message Type = Unconfirmed Data Up Direction = up FCnt = 5 FCtrl.ACK = false FCtrl.ADR = true
- 5. from lora.crypto import loramac_decrypt payload = '94A98189FFF7E89D9459C5' sequence_counter = 5 key = 'DF2FE61E548EF67A186ECFF15E2A09AB' dev_addr = '26011B8B' print(loramac_decrypt(payload, sequence_counter, key, dev_addr)) Resultobtainedbyexecutingthe payload_decrypt.py [104, 101,108, 108, 111,32, 119, 111,114, 108, 100] To convertthisbase 64 valuesto ASCIIValue,letususesanonline converter https://www.branah.com/ascii-converter