I looked for some arduino code that uses a node and a gateway, like you said… Also, thank you 
The data seens really strange… Like this @L&ɂvⵍᓻrD:"w;,ꕀ
It’s not text (aka string), it’s a sequence of numbers which we’d normally view as Hex.
For instance, MDFGMzBBNDI= is decoded as 01 F3 0A 42.
The = sign in the Base64 is padding, sometimes you’ll get 2 of them, sometimes 1, sometimes none, depends on the length of your input.
You’ll need to look at the node code to see how it puts the numbers together and what they mean.
To be clear, the packet as seen by a gateway is encrypted if it is in accordance with the LoRaWAN specification.
The encrypted packet may then also be base64 encoded for Internet interchange with a network server.
Only after the packet has been passed through the network and application servers would the payload be decrypted to reveal the original “contents” (measurements or whaver) provided to the node’s LoRaWAN stack.
In contrast, the Sandeep code at the start of the thread doing raw LoRa rather than LoRaWAN appears to load the cleartext string “hello” into the radio transmit buffer. If that where what had run (and the air settings matched the gateway’s) then what the gateway would report would be that, or its base64 representation. But in that case the gateway’s attempt to parse out LoRaWAN header fields like a device address for display would be nonsense, since that is not any sort of LoRaWAN packet.
Toinzim has been using a LoraServer on his gateway - which is why I considered the string he was looking at had been decrypted and just needed to be decoded.
Who knows precisely, too many screen shots of different tests!
I’m using the default application of RAK7258… It worked great with the arduino code, but didn’t work with the MSP430… still trying 