The specified fill mode is not valid for this algorithm - C # - System.Security.Cryptography

Question

quite new for C # and currently there is a problem with decrypting long passwords with an error

The specified key is not valid for this algorithm

I know that this is because the bit length of the encrypted passwords is not supported, but you don’t know how to use the proposed methods to use these longer passwords.

Here is my encrypt and decrypt

"cipherKey": "0123456789abcdef", "cipherVector": "Somereallycooliv"

using System;
using System.Security.Cryptography;
using System.IO;
using System.Text;

namespace DataApi
{
public class Encryption
{
    private readonly IConfigurationService _configService;


    private const string _vector = "cipherVector";
    private const string _key = "cipherKey";

    public Encryption(IConfigurationService configService)
    {
        _configService = configService;
    }
    public string EncryptString(string text)
    {
        if(string.IsNullOrEmpty(text))
        {
            return "";
        }
        try
        {

      var key = Encoding.UTF8.GetBytes(_configService.Get(_key));
        byte[] IV = Encoding.ASCII.GetBytes(_configService.Get(_vector));

        using (var aesAlg = Aes.Create())
        {
            using (var encryptor = aesAlg.CreateEncryptor(key, IV))
            {
                using (var msEncrypt = new MemoryStream())
                {
                    using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    using (var swEncrypt = new StreamWriter(csEncrypt))
                    {
                        swEncrypt.Write(text);
                    }

                    var decryptedContent = msEncrypt.ToArray();

                    var result = new byte[IV.Length + decryptedContent.Length];

                    Buffer.BlockCopy(IV, 0, result, 0, IV.Length);
                    Buffer.BlockCopy(decryptedContent, 0, result, IV.Length, decryptedContent.Length);

                    return Convert.ToBase64String(result);
                }
            }
        }
        }
        catch(Exception e) {
             Loggifer.Error("Unable to encrypt string: "+text , e );

            throw e;
        }
    }

    public string DecryptString(string cipherText)
    {
        if(string.IsNullOrEmpty(cipherText))
        {
            return "";
        }
        try
        {
            var fullCipher = Convert.FromBase64String(cipherText);

            byte[] IV = Encoding.ASCII.GetBytes(_configService.Get(_vector));
            var cipher = new byte[16];

            Buffer.BlockCopy(fullCipher, 0, IV, 0, IV.Length);
            Buffer.BlockCopy(fullCipher, IV.Length, cipher, 0, IV.Length);
            var key = Encoding.UTF8.GetBytes(_configService.Get(_key));

            using (var aesAlg = Aes.Create())
            {
                using (var decryptor = aesAlg.CreateDecryptor(key, IV))
                {
                    string result;
                    using (var msDecrypt = new MemoryStream(cipher))
                    {
                        using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                        {
                            using (var srDecrypt = new StreamReader(csDecrypt))
                            {
                                result = srDecrypt.ReadToEnd();
                            }
                        }
                    }

                    return result;
                }
            }
        }
        catch (Exception e)
        {
            Loggifer.Error("Unable to decrypt string: "+cipherText , e );
            throw e;
        }
    }

}
}

Answer 1

In function public string DecryptString(string cipherText)

two changes are required:

 var cipher = new byte[fullCipher.Length - IV.Length];

and

 Buffer.BlockCopy(fullCipher, IV.Length, cipher, 0, fullCipher.Length - IV.Length);