Need an Encryption/decryption method does not have a '/' in the encrypted string [duplicate]

Answer 1

The encryption itself simply outputs bytes, not characters. So this question is quite unrelated to encryption/decryption. Your actual problem is converting arbitrary bytes into a string that can be used in a url. I recommend using URL safe Base64 over normal Base64 for this.

Those / characters are produced by the Base64 encoding you apply to the ciphertext. Base64 uses ASCII letters and digits (62 total), plus / and + and finally = as padding.

Padding is pretty useless, so I'd strip it.

Then replace / with _ and + with -. This is called URL safe Base64 or base64url. It's described in RFC4648.

public static string Base64UrlEncode(byte[] bytes)
{
    return Convert.ToBase64String(bytes).Replace("=", "").Replace('+', '-').Replace('/', '_');
}

public static byte[] Base64UrlDecode(string s)
{
    s = s.Replace('-', '+').Replace('_', '/');
    string padding = new String('=', 3 - (s.Length + 3) % 4);
    s += padding;
    return Convert.FromBase64String(s);
}

Answer 2

If you're doing it for passing in the URL only, I suggest you generating any encrypted string (no matter if it has / or not), and do:

var sanitized = HttpUtility.UrlEncode(encryptedString);

As you can see, / becomes %2f. Then you can simply do:

var encryptedString = HttpUtility.UrlDecode(sanitized)

and you will get the same string again.

Edit: HttpUtility is in the System.Web assembly.

Answer 3

Convert.ToBase64String uses letters, numbers, + and / so you can simply switch the / out for something else that's not a letter, number or +:

Encoding:

// ...
string cipherText = Convert.ToBase64String(cipherTextBytes);
string ctWithoutSlashes = cipherText.Replace("/", "-");

Decoding

string cipherText = ctWithoutSlashes.Replace("-", "/");
// ...