C# - 암호화 (SHA256)

using System.Security.Cryptography;

public static string encryptSHA256(string plain)
        {
            try
            {
                //바이트로 변환 
                byte[] plainBytes = Encoding.UTF8.GetBytes(plain);

                SHA256Managed sm = new SHA256Managed();

                byte[] encryptBytes = sm.ComputeHash(plainBytes);

                //hex.. 16진수
                //string encryptString = BitConverter.ToString(encryptBytes).Replace("-", "").ToLower();

                //base64
                string encryptString = Convert.ToBase64String(encryptBytes);

                return encryptString;
            }
            catch (Exception)
            {
                return null;
            }
        }