Unable decrypt URL encoded Base64 String

Question

Hello thank you for reading;

I've tried to decrypt thise Base64 string in anyway possible. Also tried searching Stackoverflow and tried other methods. Every response it's just jibberish.

v6kEwElTQI%2fNlQc87zM7Od2%2fsaAghvSbCVyYaJRTf4U%3d

Hope you've got any ideas!

Why do you think it's base64, or rather, which dialect is it? Why are there `-` and `_` characters? What is the expected decoded value? — CodeCaster, Oct 06 '15 at 20:26
Same question. Why does that string contain percent-encoded values? `%2f` is `/` and `%3d` is `=`. What output do you expect? Not only strings can be base64-encoded, you know? The unencoded input / expected output may be just binary data, so "gibberish" if you try to interpret it as a string. — CodeCaster, Oct 06 '15 at 20:29
It's not a base64 string: https://en.wikipedia.org/wiki/Base64 — Reinard, Oct 06 '15 at 20:29
To be valid question for SO you need to include at least expected output, but better yet code you've tried. It could be URL encoded Base64 string - but without expected result not clear what help you expect. — Alexei Levenkov, Oct 06 '15 at 20:33
`Convert.FromBase64String(WebUtility.UrlDecode("v6kEwElTQI%2fNlQc87zM7Od2%2fsaAghvSbCVyYaJRTf4U%3d"))` runs without error, producing 32 bytes of output. But I don't have enough context to say if the output is correct or not. — CodesInChaos, Oct 06 '15 at 20:33
It's URL encoded and part of the source contained Base64 Value = unknown — TheBlinderCoder, Oct 06 '15 at 20:34

ZethMatthews · Answer 1 · 2015-10-06T20:56:01.520

It's not exactly readable, but it does successfully Base64 decode:

Firstly, I manually de-URL-encoded it. There are three URL escape sequences in there:

%2f : '/' (two of these)
%3d : '='

Giving me v6kEwElTQI/NlQc87zM7Od2/saAghvSbCVyYaJRTf4U=

With those changed, it's Base64.

Then, you can use the old methods of decoding in C# .NET:

byte[] arr = Convert.FromBase64String('v6kEwElTQI/NlQc87zM7Od2/saAghvSbCVyYaJRTf4U=');

Console.WriteLine(System.Text.Encoding.Default.GetString(arr));

// As a note, I'm using Default encoding here. Your system may use 
// a different encoding by default. Alternatively, you can replace 
// 'Default' here with ASCII or Unicode.

Using unicode I get 쀄卉轀闍㰇㏯㤻뿝ꂱ蘠鯴尉梘厔蕿 instead.

I have ruled out that it's not an image (at least in a System.Drawing.Image format.)

While decoding it was fun, I have to agree with the comments. It's important to know what the data is going to be after it's decoded since it'll only be a nameless stream of bytes at that point.

Unable decrypt URL encoded Base64 String

1 Answers1