I reverse engineered my dad’s loyalty card and found his balance sitting in plain hex (Club Afriquia card)
So my dad has this fidelity card from our town's Afriquia gaz station. You know the type — tap to pay, collect points, probably some basic NFC tag inside.
Out of curiosity, I scanned it with my phone and dumped the memory using NFC Tools.
Here’s what I got:
\`\`\`
Page 00: 04 AC 1F 3F
Page 01: 22 2B 2C 84
Page 02: A1 48 FF FF
Page 03: E1 10 06 0F
Page 04: 03 20 D1 01
Page 05: 1C 54 02 65
Page 06: 6E 30 41 71
Page 07: 4D 47 56 55
Page 08: 68 58 71 33
Page 09: 76 54 71 4C
Page 10: 2F 6E 47 54
Page 11: 51 58 64 41
Page 12: 3D 3D FE 00
\`\`\`
Looked like gibberish at first — but I noticed a base64-looking string at the end:
en0AqMGVUhXq3vTqL/nGTQXdA==
Decoded it to 18 bytes of binary:
7A 7D 00 A8 C1 95 52 15 EA DE F4 EA 2F F9 C6 4D 05 DD
Still nothing… until my dad mentioned he got the card on February 8, 2025 and it has a 10-year lifespan.
I checked the first 4 bytes as a Unix timestamp:
7A 7D 00 A8 → February 8, 2035 ✅
Then I looked at the last 2 bytes: 05 DD.
As big-endian hex, that’s 0x05DD = 1501 cents = 15.01 (Whatever currency it is stored as).
That’s literally his balance. Just sitting there. In plain sight. On an NFC tag. No encryption. No authentication.
Dont hesitate to correct me if I got something wrong 😁