C# 3DES加密与oracle 3DES加密结果比较

使用C#和oracle对同一字符串进行3DES加密为什么结果不同（key相同）？
对"aaaaaaaa"进行加密得到的结果分别如下：

C#结果为:      N0p5hwmlyn+dQUWEbvwkiHl960iEfyAd
oracle结果为:  F5ACE5DCAE43F640

C#程序:
C# code:

public static string Encrypt3DES(string a_strString, string a_strKey)
{
try
{
byte[] bt = (new System.Text.UnicodeEncoding()).GetBytes(a_strString);
PasswordDeriveBytes pdb = new PasswordDeriveBytes(a_strKey, null);
byte[] key = pdb.GetBytes(24);
byte[] iv = pdb.GetBytes(8);
MemoryStream ms = new MemoryStream();
TripleDESCryptoServiceProvider tdesc = new TripleDESCryptoServiceProvider();
CryptoStream cs = new CryptoStream(ms, tdesc.CreateEncryptor(key, iv), CryptoStreamMode.Write);
cs.Write(bt, 0, bt.Length);
cs.FlushFinalBlock();
return Convert.ToBase64String(ms.ToArray());
}
catch (Exception ex)
{
throw ex;
}
}



oracle 存储过程：
SQL code:

FUNCTION Encrypt_3k