based on the example below the node js is showing what l need and don't have power to change but need it in c#

l have node js code generates : ciph DhX6hhOUpeYZJexlMD 6zg==

const crypto = require('crypto'); 
var plainText = '124_12344612'; 
var keys ="gjOMA9mMihhOANN4erqksLIaHzDZWP0shFayUU39C0A="; //password/
  
var hash = Buffer.from(keys, 'base64');
 
var iv = Buffer.from([0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]);
 
var cipher = crypto.createCipheriv('aes-256-cbc',hash,Buffer.from(iv, 'utf8'));
 
var ciph = cipher.update(plainText,'utf8','base64');

ciph  =cipher.final('base64')
 
console.log("ciph" ,ciph)

this is the c# code generates : nXU8XunpCy6OhiM251qcqg==

     private const int AesKeySize = 16;
   static void Main(string[] args)
        {  
            string password =  "gjOMA9mMihhOANN4erqksLIaHzDZWP0shFayUU39C0A="; 
            string message = "124_12344612";
           

            // Create sha256 hash
            SHA256 mySHA256 = SHA256Managed.Create();
            byte[] key = mySHA256.ComputeHash(Encoding.ASCII.GetBytes(password));

            // Create secret IV
            byte[] iv = new byte[16] { 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0 };

            string encrypted = EncryptString(message, key, iv);
            string decrypted = DecryptString(encrypted, key, iv);
          
            Console.ReadLine();
        }
        public static string EncryptString(string plainText, byte[] key, byte[] iv)
        {
            // Instantiate a new Aes object to perform string symmetric encryption
            Aes encryptor = Aes.Create();

            encryptor.Mode = CipherMode.CBC;

            // Set key and IV
            byte[] aesKey = new byte[32];
            Array.Copy(key, 0, aesKey, 0, 32);
            encryptor.Key = aesKey;
            encryptor.IV = iv;

            // Instantiate a new MemoryStream object to contain the encrypted bytes
            MemoryStream memoryStream = new MemoryStream();

            // Instantiate a new encryptor from our Aes object
            ICryptoTransform aesEncryptor = encryptor.CreateEncryptor();

            // Instantiate a new CryptoStream object to process the data and write it to the 
            // memory stream
            CryptoStream cryptoStream = new CryptoStream(memoryStream, aesEncryptor, CryptoStreamMode.Write);

            // Convert the plainText string into a byte array
            byte[] plainBytes = Encoding.ASCII.GetBytes(plainText);

            // Encrypt the input plaintext string
            cryptoStream.Write(plainBytes, 0, plainBytes.Length);

            // Complete the encryption process
            cryptoStream.FlushFinalBlock();

            // Convert the encrypted data from a MemoryStream to a byte array
            byte[] cipherBytes = memoryStream.ToArray();

            // Close both the MemoryStream and the CryptoStream
            memoryStream.Close();
            cryptoStream.Close();

            // Convert the encrypted byte array to a base64 encoded string
            string cipherText = Convert.ToBase64String(cipherBytes, 0, cipherBytes.Length);
             

            // Return the encrypted data as a string
            return cipherText;
        }

how do l alter the c# code l have written to return : DhX6hhOUpeYZJexlMD 6zg== same as the node js

thank you Thomas Weller/jdweng/Lukas Hein it works based on your provided solution : updated code

  static void Main(string[] args)
        {
          
            string password = "gjOMA9mMihhOANN4erqksLIaHzDZWP0shFayUU39C0A"; 
            string message = "124_12344612";

            byte[] key = Convert.FromBase64String(password);

            // Create secret IV
            byte[] iv = new byte[16] { 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0 };

            string encrypted = EncryptString(message, key, iv);
            string decrypted = DecryptString(encrypted, key, iv);
          
            Console.ReadLine();
        }

public static string EncryptString(string plainText, byte[] key, byte[] iv)
        {
            // Instantiate a new Aes object to perform string symmetric encryption
            Aes encryptor = Aes.Create();

            encryptor.Mode = CipherMode.CBC;

            // Set key and IV
            byte[] aesKey = new byte[32];
            Array.Copy(key, 0, aesKey, 0, 32);
            encryptor.Key = aesKey;
            encryptor.IV = iv;
            //encryptor.Padding = PaddingMode.Zeros;
            //encryptor.Padding = PaddingMode.ISO10126;
            //encryptor.Padding = PaddingMode.ANSIX923;
            encryptor.Padding = PaddingMode.PKCS7;

            // Instantiate a new MemoryStream object to contain the encrypted bytes
            MemoryStream memoryStream = new MemoryStream();

            // Instantiate a new encryptor from our Aes object
            ICryptoTransform aesEncryptor = encryptor.CreateEncryptor();

            // Instantiate a new CryptoStream object to process the data and write it to the 
            // memory stream
            CryptoStream cryptoStream = new CryptoStream(memoryStream, aesEncryptor, CryptoStreamMode.Write);

            // Convert the plainText string into a byte array
            byte[] plainBytes = Encoding.UTF8.GetBytes(plainText);

            // Encrypt the input plaintext string
            cryptoStream.Write(plainBytes, 0, plainBytes.Length);

            // Complete the encryption process
            cryptoStream.FlushFinalBlock();

            // Convert the encrypted data from a MemoryStream to a byte array
            byte[] cipherBytes = memoryStream.ToArray();

            // Close both the MemoryStream and the CryptoStream
            memoryStream.Close();
            cryptoStream.Close();

            // Convert the encrypted byte array to a base64 encoded string
            string cipherText = Convert.ToBase64String(cipherBytes, 0, cipherBytes.Length);
             

            // Return the encrypted data as a string
            return cipherText;
        }

CodePudding user response：

By hashing your password you actually use another key. Just use byte[] key = Convert.FromBase64String(password);