Why does this encrypted string have funny characters in it? It isn't readable?

问题

I'm converting the encrypted text using UTF8, yet the resulting string has funny characters that I can't read and not sure if I can send this text to the browser.

        string message = "hello world";
        var rsa = new RSACryptoServiceProvider(2048);

        var c = new UTF8Encoding();

        byte[] dataToEncrypt = c.GetBytes(message);
        byte[] encryptedData = rsa.Encrypt(dataToEncrypt, false);

        string output = c.GetString(encryptedData);

        Console.WriteLine(output);
        Console.ReadLine();

When I run the above, I get the following:

�VJI����J/;�>�:<�M����g�1�7�A.@�`J�s��~��)�Fn�����5�.���o���ҵ���jH3;G�<<��F�͗��~?�Y�#���j���6l{{�Y�$�]���nylz���X8u�\f�V1/�$�n+�\b��\b�fsAh՝G\n�\t���\b���6߇3����Ԕ���4��@هhI���'\0� T�n��|EϺ^7ú l��T\\!�w���QRWA%p��V\f��5�

I need to send this text back to the browser, or save it to a file and currently I'm not sure why I am getting these characters?

回答1:

The problem is that you are taking an array of bytes that was not created by encoding text, and use it as if it was. You can only decode data that was created by encoding, if you decode any arbitrary data, you end up with garbage.

If you want the binary data produced by the encryption as a string, use for example base64 encoding:

string output = Convert.ToBase64String(encryptedData);

When you want to decrypt the data, use Convert.FromBase64String to get the byte array back, decrypt it, and use Encoding.UTF8.GetString to turn it back into the original string. There it will work do decode the data, because it was created by encoding the string from the beginning.

回答2:

These two lines are pretending that the output of an RSA-encrypted UTF-8 sequence is a valid UTF-8 sequence:

    var c = new UTF8Encoding();
    string output = c.GetString(encryptedData);

But this is simply not the case: the RSA encryption maps byte values to other, (seemingly) arbitrary byte values. The resulting byte sequence doesn’t form a valid UTF-8 sequence (there is no reason to assume that it would), and thus cannot be treated as one.

If you merely want a readable (or HTTP sendable) representation of your data, then Base64 is the way to go, as shown in other answers. Fundamentally, though, you should probably read Joel’s article about The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!).

回答3:

Encrypting a string will result in a byte array that contains non-printable characters. You'll want to convert it to base64 to have a readable version of it.

来源：https://stackoverflow.com/questions/16950162/why-does-this-encrypted-string-have-funny-characters-in-it-it-isnt-readable

标签

encoding

cryptography

rsa