Util.cs

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

namespace NetCoreAngular
{
    public class Util
    {
        byte[] keyByte = null;
        public Util(byte[] b)
        {
            keyByte = b;
        }
        public string cifrar(string cadena, string clave)
        {
            // Get the bytes of the string
            byte[] bytesToBeEncrypted = Encoding.UTF8.GetBytes(cadena);
            byte[] passwordBytes = Encoding.UTF8.GetBytes(clave);

            // Hash the password with SHA256
            passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

            byte[] bytesEncrypted = AES_Encrypt(bytesToBeEncrypted, passwordBytes);

            string result = Convert.ToBase64String(bytesEncrypted);

            return result;
        }

        public string desCifrar(string cadena, string clave)
        {
            // Get the bytes of the string
            byte[] bytesToBeDecrypted = Convert.FromBase64String(cadena);
            byte[] passwordBytes = Encoding.UTF8.GetBytes(clave);
            passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

            byte[] bytesDecrypted = AES_Decrypt(bytesToBeDecrypted, passwordBytes);

            string result = Encoding.UTF8.GetString(bytesDecrypted);

            return result;
        }

        public byte[] AES_Encrypt(byte[] bytesToBeEncrypted, byte[] passwordBytes)
        {
            byte[] encryptedBytes = null;

            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 256;
                    AES.BlockSize = 128;

                    var key = new Rfc2898DeriveBytes(passwordBytes, keyByte, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    AES.IV = key.GetBytes(AES.BlockSize / 8);

                    AES.Mode = CipherMode.CBC;

                    using (var cs = new CryptoStream(ms, AES.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeEncrypted, 0, bytesToBeEncrypted.Length);
                        cs.Close();
                    }
                    encryptedBytes = ms.ToArray();
                }
            }

            return encryptedBytes;
        }
        public byte[] AES_Decrypt(byte[] bytesToBeDecrypted, byte[] passwordBytes)
        {
            byte[] decryptedBytes = null;


            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 256;
                    AES.BlockSize = 128;

                    var key = new Rfc2898DeriveBytes(passwordBytes, keyByte, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    AES.IV = key.GetBytes(AES.BlockSize / 8);

                    AES.Mode = CipherMode.CBC;

                    using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeDecrypted, 0, bytesToBeDecrypted.Length);
                        cs.Close();
                    }
                    decryptedBytes = ms.ToArray();
                }
            }

            return decryptedBytes;
        }

    }
}