How to choose an encryption algorithm to encrypt/decrypt a file?

Recently I am writing a QT program that require me to encrypt/decrypt a file. I am new to encryption where I am totally don't know anything on how to do encryption using programming. After googling a while, I found this thread which is very similar to my objective. They suggest to use crypto++, but my problem is when I reach there, there 开发者_开发问答are plenty of selection for encryption. I just want to encrypt a file, doesn't need a sophisticate one, and don't need a password to open the file. Only my program can open and read that file.

May I know how to choose the encryption algorithm that is suite for me?

THanks @!

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Maybe a short (very short) intro to cryptographic algorithms would be helpful:

• Symmetric encryption: uses the same key to encrypt and decrypt. Examples include DES, AES, and Blowfish.
• Asymmetric encryption: requires a certain key to encrypt (public), and a different key to decrypt (private). Examples include RSA, DSA, and ElGamal

For this application I'd suggest a symmetric algorithm, AES would probably be a good fit (AES256). Regardless of what you use though, there will always be a key (otherwise it wouldn't be very good encryption). The simple approach would be storing the password directly in the program. This would allow your users to avoid typing anything, but a determined attacker could easily find the password even in a compiled binary.

This is about as specific as I can get unless you provide further details. I hope this helps.

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Given the explanation of purpose in your reply to my comment on the question, it seems like there's little point going beyond low-level obfuscation of the XML. You could, for example, simply XOR the file content with an arbitrary value (e.g. AA hex), or a small number of values that you use on successive characters (AA, 23, B7, ...), then loop to use AA again. Doesn't sound like there's much benefit in using a real encryption library: anyone that determined to screw up their software's operation will find a way anyway....

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Simplest 'real' symmetric algorithm is probably blowfish, there is sample code in 'c' and'c++' which is very easy to integrate into your code

There is an independant QCrypto lib (not part of the main Qt src) but it's possibly a little more complicated than you need