> For the complete documentation index, see [llms.txt](https://codingmace.gitbook.io/masterward/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://codingmace.gitbook.io/masterward/ctf/2019/crypto-2019.md).

# Crypto CTF 2019

## Decode Me! - Crypto \[122 pts] <a href="#decode-me" id="decode-me"></a>

> &#x20;**Decode me!** D: mb xwhvxw mlnX 4X6AhPLAR4eupSRJ6FLt8AgE6JsLdBRxq57L8IeMyBRHp6IGsmgFIB5E :ztey xam lb lbaH

I reversed the string because it looked like it needed and got `Habl bl max yetz: E5BIFgmsGI6pHRByMeI8L75qxRBdLsJ6EgA8tLF6JRSpue4RALPhA6X4 Xnlm wxvhwx bm :D` \
Which by the smiley face I know I did something right. I did rot and closest I found was ROT7\
`Ohis is the flag: L5IPMntzNP6wOYIfTlP8S75xeYIkSzQ6LnH8aSM6QYZwbl4YHSWoH6E4 Eust decode it :K`\
Some of that was right but the middle was not base64  and capital was wrong so I went back and checked to get the first letter to T and that was ROT12\
`This is the flag: Q0NURntzSU1wTDNfYlU3X20xeDNkXzV1QnM3aXR1VDEwbl9DMXBoM1J9 Just decode it :P`\
And finally, decode it using base64. Below is the code that helped me do all this.

```python
cipher = "D: mb xwhvxw mlnX 4X6AhPLAR4eupSRJ6FLt8AgE6JsLdBRxq57L8IeMyBRHp6IGsmgFIB5E :ztey xam lb lbaH"
print("Original Cipher: ", cipher)
cipher = cipher[::-1]
print("Cipher Reversed: ", cipher)
decoded_cipher = ""

for i in range(len(cipher)):
    val = ord(cipher[i])
    if cipher[i].isupper():
        val += 12
        if val > ord('Z'):
            val -= 26
        decoded_cipher += chr(val)
    elif cipher[i].islower():
        val += 7
        if val > ord('z'):
            val -= 26
        decoded_cipher += chr(val)
    elif cipher[i].isdigit():
        val = ord('0') + (int(cipher[i])+ 5) % 10
        decoded_cipher += chr(val)
    else:
        decoded_cipher += cipher[i]

print(decoded_cipher)
```

**Flag: CCTF{sIMpL3\_bU7\_m1x3d\_5uBs7ituT10n\_C1ph3R}**


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