Access Denied 1.2 CTF 2018: Another Riddle to solve (Cryptography)

Challenge

Francis Bacon once told me “I have your flag. Ask me nicely and I shall give you the flag.”

Download file from : https://accessd.sfo2.digitaloceanspaces.com/crypto150.txt

Solution

Considering the quote of Francis Bacon, the Bacon’s cipher must be involved.

The content of the downloaded file is the following:

QUFBQUFBQUFCQUFBQUJBQUFCQUFCQUFBQkJBQUFCQUFBQkJBQUJBQUFCQkFBQUJBQUFBQUJBQUFBQUJCQUFBQkJBQUJBQUFCQUJBQUJBQUFBQXtBQkFBQkFBQUFCQkFCQkFBQkJCQUFBQkFBQUFCQUFBQUFBQUFCQUFCQkFCQUJCQUFBQUFCQkFBQkFBQUJBQkFBQkFBQUFBQUJBQUJBQUFBQkJBQkJBQUJCQkFBQUJBQkJCQUFCQkFCQUJBQUFBQkJBQUJBQUJBQkFBQUJ9

But it doesn’t seem a text encoded with Bacon’s cipher. It is a Base64 encoded text, so the first step is to decode it.

AAAAAAAABAAAABAAABAABAAABBAAABAAABBAABAAABBAAABAAAAABAAAAABBAAABBAABAAABABAABAAAAA{ABAABAAAABBABBAABBBAAABAAAABAAAAAAAABAABBABABBAAAAABBAABAAABABAABAAAAAABAABAAAABBABBAABBBAAABABBBAABBABABAAAABBAABAABABAAAB}

Now the text can be decoded using an on-line tool.

The flag is:

ACCESSDENIED{DELICIOUSBACONDELICIOUSPOINTS}

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