Context: I was given a piece of encrypted string to decipher and I have been stuck at it for a while. To not ruin the point of the problem, I will provide only some description of the text and my attempts at deciphering it. In doing so, I hope that more experienced people can give me some pointers and hints on the nature of the ciphertext.
In first glance I determined that the ciphertext (~150 characters) is most likely base64-encoded, since it is alphanumeric and ends with an equals sign. However, decoding it in either ASCII or utf-8 results in a meaningless string composed mostly of unicode. The unicode characters can all be represented in format U+000X or U+001X where X is a digit or letter.
More importantly, I noticed a pattern in the decoded text: certain groups of alphabetical letters recur once 12 or 24 letters. This reminds me of Vigenere cipher, but I cannot do anything with it with all the nonsense unicode scattered around the text.
This probably means that decoding the text in base64 points somewhere around the right direction, but perhaps I need to try other ways of decrypting the binary? Or perhaps I need to apply more operations on the decoded text? Any advice on what I can try next is greatly appreciated.
EDIT: Now that I was thinking about it, it could possibly be an XOR cipher. So I'll try that.