DES oracle 如何解密 c# 中的等效项

Question

I have this function on oracle db:

BEGIN
    key_raw := utl_i18n.string_to_raw(key,'AL32UTF8');
    plaintext := dbms_crypto.decrypt(
    src => chipertext,
    typ => dbms_crypto.DES_CBC_PKCS5,
    key => key_raw
    );
    return utl_i18n.raw_to_nchar(plaintext,'AL32UTF8');
END 

and need to implement in c#.Net

this what I've Done:

public static string DecryptDES(string strData,string skey)
        {
            byte[] clearData = Encoding.UTF8.GetBytes(strData);
            byte[] key = Encoding.UTF8.GetBytes(skey);
            DES desDecrypt = new DESCryptoServiceProvider();
            desDecrypt.Mode = CipherMode.CBC;
            desDecrypt.Padding = PaddingMode.PKCS7;
            desDecrypt.Key = key;
            ICryptoTransform transForm = desDecrypt.CreateDecryptor();
            MemoryStream decryptedStream = new MemoryStream();
            CryptoStream cryptoStream = new CryptoStream(decryptedStream, transForm, CryptoStreamMode.Write);
            cryptoStream.Write(clearData, 0, clearData.Length);
            cryptoStream.FlushFinalBlock();
            byte[] plain = decryptedStream.ToArray();
            return Encoding.UTF8.GetString(plain);
        }

in oracle that function called like this:

select decrypt('BEB9B507432B91E116EC3F07364E38C5', 'testtesttest') from dual;

when this method call in c#:

DecryptDES("BEB9B507432B91E116EC3F07364E38C5", "testtesttest")

it's return error:

System.ArgumentException: 'Specified key is not a valid size for this algorithm.'

also I tried another key and chipertext and it's return bad data.

I believe this is something to do with data format, since it's return error on c#, any suggestion?

Answer 1

What's wrong is that your ciphertext input in C# is a string. Ciphertext (your chipertext , ugh) is binary (or "RAW" in Oracle speak). There should be no UTF-8 conversion to / from the ciphertext, because that may lead to missing data.

You'll probably have to use the first 7 or 8 bytes of the UTF-8 encoded key for DES. Yuk.