For this challenge we have a file that contains the following string:
YmVnaW4gNjQ0IDxkYXRhPiA2MURRITFVXU48JjFLODZNVzpWLUk5Jk1EPiYlQSJAYGAgYCBlbmQK
After analysis, I could determinate that the string is encoded in base64.
Once decoded I got the following string:
begin 644 <data> 61DQ!1U]N<&1K86MW:V-I9&MD>&%A"@`` ` end
It seems to be readable text but a small part of it is still encoded, so I googled the meaning of "begin 644 ".
And it seems that our piece of text is encoded in UUencode.
On the Wikipedia page I found the UUencode table.
Based on the UUencode table I made a script to decrypt the message.
And here is the flag FLAG_npdkakwkcidkdxaa