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How to decrypt a string with unknown encryption algorithm?

There is a string:

5aaC5p6c5L2g5a+55oiR5Lus5Zyo5YGa55qE5LqL5oOF5pyJ5YW06Laj77yM5bm25LiU5a+5cmFpbHMv5YmN56uv5byA5Y+R5pyJ6Ieq5L+h77yM5qyi6L+O5Y+R6YCB6YKu5Lu25YiwZ2hvc3RtNTVAZ2l0Y2FmZS5jb23pooTnuqbkuqTmtYHml7bpl7TvvIznoa7lrprkuYvlkI7lj6/ku6Xnm7TmjqXmnaXliLDmiJHku6znmoTlt6XkvZzlrqTlj4Lop4LkuqTmtYHvvIzosKLosKIK

I don't know the encryption algorithm. How to decrypt it?

To analyze and solve this problem, what should I learn?

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    Well, you weren't really meant to ask for help, gelosie. Hope you have a good interview, though. :) Commented Jan 22, 2013 at 1:50
  • Yeah, was just about to comment that: If you are interested in what we do, and rails / front-end development, self-confidence, welcome to send mail to the appointment [email protected] exchange time, can be determined directly to our studio visit exchanges, thank you Commented Jan 22, 2013 at 1:51
  • @MichaelPetrotta :-( I saw this string in gitcafe.com which is copy of github.com in China. I have not study encode/decode or encryption. My key point question is the last one: To analyze and solve this problem, what should I learn? Thank you very much for All . Commented Jan 22, 2013 at 1:58
  • If it actually was encrypted with a valid encryption algorithm, you'd need at least the key, too (or a couple of decades for the encryption to be breakable by cryptanalysis/brute force). And may be representation details. Maybe a salt. Commented Jul 29, 2017 at 19:20

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It's not an encryption algorithm, it's base64. You can tell because of the +s.

http://www.opinionatedgeek.com/dotnet/tools/base64decode/

Try running it through this page, it'll turn into this:

如果你对我们在做的事情有兴趣，并且对rails/前端开发有自信，欢迎发送邮件到[email protected]预约交流时间，确定之后可以直接来到我们的工作室参观交流，谢谢

NOTE: If it was actually encrypted and you actually had no clue what it was encrypted with, you would be screwed, because any good encryption algorithm turns the output into meaningless gibberish, unusable without the key. Base64 has no key, you can just reverse it the same way every time.

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I came here to say that, +1. I managed to successfully encrypt the string by running that through Google translate though :-S. Roughly, it's an advert for a rails dev shop.
Well, I did once see a base 64 encryption which was using a different alphabet, basically turning it into a substitution cipher, but I don't think that one counted.
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This string appears to be a Base64 encoded string.

The decoded value is: 如果你对我们在做的事情有兴趣，并且对rails/前端开发有自信，欢迎发送邮件到[email protected]预约交流时间，确定之后可以直接来到我们的工作室参观交流，谢谢

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Well, the string is likely Base64 encoded. If you decode it, you should get an effectively random piece of binary data if its encrypted (EDIT: As others have shown, it isn't encrypted, but the following would still apply if it were)

By checking the length, you can determine the block-size of the cipher. If its not an even block size, it likely could be a stream cipher (or a block cipher operated in stream mode).

However, any more information will need to be gleamed from other sources - as the point of good encryption is to make the data truly opaque.

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Its Base 64 encryption.The above code is translated as:

如果你对我们在做的事情有兴趣，并且对rails/前端开发有自信，欢迎发送邮件到[email protected]预约交流时间，确定之后可以直接来到我们的工作室参观交流，谢谢

"If you are doing things we are interested in, and on the rails / front-end developers are confident, please send e-mail to communicate [email protected] appointment time, after determining the direct exchange of visits to our studio, thank you"

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