# pip install msgpack 
import msgpack
import base64

card_data = {
    "card": 12345678900000,
    "pin": "1a2b3c"
}

packed = msgpack.packb(card_data)
encoded = base64.b64encode(packed)

# https://gchq.github.io/CyberChef/#recipe=To_MessagePack()To_Base64('A-Za-z0-9%2B/%3D')&input=ewogICAgImNhcmQiOiAxMjM0NTY3ODkwMDAwMCwKICAgICJwaW4iOiAiMWEyYjNjIgp9&oeol=VT