Cipher Cascade Reverse, Base64, hex, ROT13

crypto
flag hiCTF{l4y3r_by_l4y3r_unw1nd}

Category: crypto / misc · Artifact: extracted/cipher_cascade.txt

What it is

=== INTERCEPTED TRANSMISSION === with the hint:

output 
Hint: The outermost layer is reversed.
Layers applied (outermost to innermost): Reverse -> Base64 -> Hex -> ???
Encoded message:
=Q2NxcTM2EzMhZTM2gjNmVTN2MzMjZDNzkzNmVzY2YmNmVTN2MzMjZDNzkzNidzM1cDNwUjN3UzN

Solve

Peel the layers literally, in order:

  1. Reverse the whole encoded string.
  2. Base64-decode it.
  3. Hex-decode the result -> ASCII uvPGS{y4l3e_ol_y4l3e_haj1aq}.
  4. The final ??? layer is ROT13 -> hiCTF{l4y3r_by_l4y3r_unw1nd}.
bash 
1python3 - <<'EOF'
2import base64
3s="=Q2NxcTM2EzMhZTM2gjNmVTN2MzMjZDNzkzNmVzY2YmNmVTN2MzMjZDNzkzNidzM1cDNwUjN3UzN"
4r=s[::-1]
5h=base64.b64decode(r).decode()            # 75765047537b...  (hex text)
6import codecs
7print(codecs.decode(bytes.fromhex(h).decode(), 'rot13'))
8EOF

Flag

output 
hiCTF{l4y3r_by_l4y3r_unw1nd}