Question Code error

[Compiler]

Hi everyone,
Can you help me find what conceptual problems exist in this exam question (regardless of library definitions):

string oneWayEncode(string plaintextPassword) {
   try {
      var digest = new SHA256Managed();
      digest.Initialize();
      //plaintextPassword = string.Concat(plaintextPassword, "salt.");
      byte[] data = digest.ComputeHash(System.Text.Encoding.UTF8.GetBytes(plaintextPassword));
      return Convert.ToBase64String(data);
   } catch (ArgumentNullException e) {
   } catch (ObjectDisposedException e) {
   }
}
 
bool login(string username, string password) {
   string storedPassword = db.lookupField(username, "password");
   return oneWayEncode(password) == oneWayEncode(storedPassword);
}

 

[jmcilhinney]

Perhaps you could tell us what you think and why and we can see whether we agree.