How to use "Cryptography.Aes" create string without special character?

Question

I call this function EncryptStringToBytes_Aes to encrypt ID, when I convert to Base64 string, it looks like that: "Zr3EChQwtq1Wl/XLhBGSIZnHI098DKJaeujDmFfS25s="; "rGp5t04HgiKSkM10ImhOEwXZTc/eawOwlZTySRp6ZMk=", how to create string without "/" or "=", later I have to decrypt the ID.

  string original = "IDNumber";

                // Create a new instance of the AesCryptoServiceProvider
                // class.  This generates a new key and initialization 
                // vector (IV).
                using (AesCryptoServiceProvider myAes = new AesCryptoServiceProvider())
                {
                      Console.WriteLine("Original:   {0} \n", original);
                    // Encrypt the string to an array of bytes.
                    byte[] encrypted = EncryptStringToBytes_Aes(original, myAes.Key, myAes.IV);
                                    
                    Console.WriteLine("Encrypted:   {0} \n", Convert.ToBase64String(encrypted));
                    
                }


     static byte[] EncryptStringToBytes_Aes(string plainText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            if (plainText == null || plainText.Length <= 0)
                throw new ArgumentNullException("plainText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("IV");
            byte[] encrypted;
            // Create an AesCryptoServiceProvider object
            // with the specified key and IV.
            using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
            {
                aesAlg.Key = Key;
                aesAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for encryption.
                using (MemoryStream msEncrypt = new MemoryStream())
                {
                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                        using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                        {

                            //Write all data to the stream.
                            swEncrypt.Write(plainText);
                        }
                        encrypted = msEncrypt.ToArray();
                    }
                }
            }


            // Return the encrypted bytes from the memory stream.
            return encrypted;

        }


        static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            if (cipherText == null || cipherText.Length <= 0)
                throw new ArgumentNullException("cipherText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("IV");

            // Declare the string used to hold
            // the decrypted text.
            string plaintext = null;

            // Create an AesCryptoServiceProvider object
            // with the specified key and IV.
            using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
            {
                aesAlg.Key = Key;
                aesAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for decryption.
                using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                {
                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        {

                            // Read the decrypted bytes from the decrypting stream
                            // and place them in a string.
                            plaintext = srDecrypt.ReadToEnd();
                        }
                    }
                }

            }

            return plaintext;

        }

You use Base64, but don't want to use Base64 because of the `/` and `=`? Are you looking for something called "base64url"? — Progman, Sep 13 '22 at 23:46
It's unclear exactly what you are trying to do here. `/` is the 63 "digit" in base64 - it conveys information. Not having it would be like trying to have decimal numbers without `9`. The `=` can be omitted easily enough as they are just padding. — moreON, Sep 13 '22 at 23:47
What is considered a special character for your purposes? Would `_` and `-` be special? — Ry-, Sep 14 '22 at 00:03
Thank Progman, you are right, I found the solution here: https://stackoverflow.com/questions/26353710/how-to-achieve-base64-url-safe-encoding-in-c — Stephen, Sep 19 '22 at 23:52

Stephen · Accepted Answer · 2022-09-20T00:51:38.247

1

Thank you "Progman", you are smart, fixed my problem.

Now use class Base64UrlEncoder from namespace Microsoft.IdentityModel.Tokens

const string StringToEncode = "Zr3EChQwtq1Wl/XLhBGSIZnHI098DKJaeujDmFfS25s=";

var encodedStr = Base64UrlEncoder.Encode(StringToEncode);
var decodedStr = Base64UrlEncoder.Decode(encodedStr);

edited Sep 20 '22 at 00:51

answered Sep 20 '22 at 00:36

Stephen

115
10

1

It sure is a weird namespace for such a universal class. – Poul Bak Sep 20 '22 at 01:44

How to use "Cryptography.Aes" create string without special character?

1 Answers1