Tags: misc
Rating:
# emoji
**Event:** Nullcon Goa HackIM 2026 CTF
**Category:** Misc
**Points:** 50
## Overview
The challenge hides a message in Unicode Variation Selectors appended to a visible emoji. These selectors are usually invisible, making them useful for steganography.
## Encoding Scheme
The hidden bytes are encoded using the Variation Selectors Supplement range:
- Range: `U+E0100` to `U+E01EF`
- For each selector:
```
byte = (codepoint - 0xE0100) + 16
```
That produces a byte stream that can be decoded as ASCII/UTF-8.
## Decoder (Python)
Paste the full emoji string into `s`.
```python
def decode_vs(s: str) -> bytes:
out = bytearray()
for ch in s:
cp = ord(ch)
if 0xE0100 <= cp <= 0xE01EF:
out.append((cp - 0xE0100) + 16)
return bytes(out)
# s = "<paste the full string here>"
data = decode_vs(s)
print("RAW BYTES:", data)
try:
print("ASCII/UTF-8:", data.decode("utf-8"))
except UnicodeDecodeError:
print("Not UTF-8. HEX:", data.hex())
```
## Flag
```
ENO{EM0J1S_UN1COD3_1S_MAG1C}
```
