Tags: basecrack base32
Rating:
# Ladder
## Task
You must attack all enemy BASEs, start low and move your way up.
File: enc.txt (in Ladder.zip)
Tags: cryptography
## Solution
The file contains base32. We can assume it's not just b64decode(b32decode(content)). Thankfully there is a tool called `basecrack`: https://github.com/mufeedvh/basecrack
```bash
$ cat enc.txt | python basecrack.py -m
[>] Enter Encoded Base:
[-] Iteration: 1
[-] Heuristic Found Encoding To Be: Base32
[-] Decoding as Base32: 3ujJnYq1YPYVouAmFC24c36quqhmGkcm5LL5mZGvs6w4mewG9Cg3jLhWJgcdMyT1EM1ZYp2cCabt6syu9oAnjLeoDkiJKgS7
[-] Iteration: 2
[-] Heuristic Found Encoding To Be: Base58
[-] Decoding as Base58: B3ubcEe7waVuE55z96FTrO8JvfuevhFXEhXqzkWINOiIaRd4OlGLhL5jgqUXaQRwNC0CXl
[-] Total Iterations: 2
[-] Encoding Pattern: Base32 -> Base58
[-] Magic Decode Finished With Result: B3ubcEe7waVuE55z96FTrO8JvfuevhFXEhXqzkWINOiIaRd4OlGLhL5jgqUXaQRwNC0CXl
[-] Finished in 0.0018 seconds
```
Hm, maybe I was wrong? Let's try it with CyberChef.
Just use all `From Base` tools available under the section `Data format`.
That works and we get the flag: `RaziCTF{w3_G0t_4ll_tHe_Ba$3s}`
But why did basecrack fail? GitHub page states: `Decode Base16, Base32, Base36, Base58, Base62, Base64, Base64Url, Base85, Base91, Base92`
Turns out there is an issue with base62: https://github.com/mufeedvh/basecrack/issues/4
I fixed that locally, still no luck.
`Encoding Pattern: Base32 -> Base58 -> Base62 -> Base64 -> Base92`
We are missing Base85 here. Debugging the script I found this:
`bad base85 character at position 36` - this is a `/`
As it turns out there is Base85 and Ascii85 and Ascii85 is not supported. After adding this (it's contained in the python base64 module) it works.
```
[-] Encoding Pattern: Base32 -> Base58 -> Base62 -> Base64 -> Ascii85
[-] Magic Decode Finished With Result: RaziCTF{w3_G0t_4ll_tHe_Ba$3s}
```
