DES encryption takes only 40 character data as a plain text

See more:

.NET3.5

C#

.NET

encryption

Hi all,
I am using aladin etoken for encryption.
I have stored DES key in etoken.
My code is running nicely when i m giving plain text with 40 characters.
It encrypt and decrypt perfectly.
but when i m giving characters more or less than 40.it is failing for me
I m using PKCS11 code. Dot net dll comes with aladin sdk only.
my code is as below.

public void encryptDES(byte[] src)
       {
           try
           {
               PKCS11.Object[] hkey = new PKCS11.Object[0];
               PKCS11.Initialize("etpkcs11.dll");

               PKCS11.Slot[] sl = new PKCS11.Slot[0];
               sl = PKCS11.GetSlotList(false);
               PKCS11.Slot sl1 = new PKCS11.Slot();
               sl1 = sl[0];

               sc = PKCS11.OpenSession(sl1, 6);

               int a = sc.Login(1, "Inspira@123");
               Console.WriteLine("Sucessfully Logged In");


               PKCS11.Mechanism[] mh1 = new PKCS11.Mechanism[500];
               mh1 = PKCS11.GetMechanismList(sl1);
               PKCS11.Mechanism mch2 = new PKCS11.Mechanism();


               byte[] IV = { 12, 13, 14, 15, 16, 17, 18, 19 };
               mch2.id = 289;
               mch2.iv = IV;
               mch2.length = IV.Length;
               PKCS11.Attribute[] pDESTemplate = new PKCS11.Attribute[2];

               pDESTemplate[0] = new PKCS11.Attribute(PKCS11.CKA_KEY_TYPE, 19);
               pDESTemplate[1] = new PKCS11.Attribute(PKCS11.CKA_CLASS, 4);

               hkey = sc.FindObjects(pDESTemplate);
               PKCS11.Object bj = new PKCS11.Object();
               bj = hkey[0];


               //Encrypt
               byte[] enct = sc.Encrypt(mch2, bj, src);
               File.WriteAllBytes("D:\\Encrypted.txt", enct);
               Console.WriteLine("Encryped text :" + ASCIIEncoding.ASCII.GetString(enct));

               Console.ReadLine();
             //  sc.Close();


           }
           catch (Exception ex)
           {
               Console.WriteLine("Error:" + ex.Message + ex.InnerException);
           }
       }

if anyone has any idea about this please help me..
It happens with tripledes also.
and also i m not able to find error code list for pkcs 11 standard by which i can come to know what is actually the error is.

Thanks in advance,
God bless u all .:)