Error while encrypting the xml file using asymmetric cipher...pls help

Question

i am encryption the xml file using asymmetric cyper....
in one class , i am generating private key and public key using "RSA" algorithm..using 1024 byte initialization...
it is generating properly...
and after that in second class i am encrypting the xml file using "DESede" algorithm and i am using public key of above class..
but i am getting exceptione :
java.security.InvalidKeyException: Invalid key length: 162 bytes
at com.sun.crypto.provider.DESedeCipher.engineGetKeySize(DashoA6275)
at javax.crypto.Cipher.init(DashoA6275)
at XmlEncryption.getEncryptedData(XmlEncryption.java:147)
at XmlEncryption.encryptCompleteXmlFile(XmlEncryption.java:123)
at demoXmlEncApp.simulateBookSellersEnd(demoXmlEncApp.java:72)
at demoXmlEncApp.main(demoXmlEncApp.java:29)
so, what is that ?
i want to use RSA algo for key generatiion and DESede for cipher initialization .
is there any site for where source code of xml file encryption using asymmetric cipher is available?
pls, help me.....

Answer 1

Sachin,
What sabre150 is trying to explain to you, is that encrypting data (such as an XML file) is a 2-step process. In the first step, you generate a symmetric key (such as DES, 3DES, AES) and encrypt your file with this key (and the appropriate mode and padding).
In order to ensure that your encrypted data cannot be decrypted by unauthorized individuals, you now need to protect the symmetric key. Encrypting your symmetric key with another symmetric key does not solve the problem, since you have a chain of symmetric keys that need to be encrypted into infinity.
Cryptographers solve this problem by encrypting the symmetric key with an asymmetric key, such as as RSA. To perform this second step, you generate an RSA key-pair, encrypt the symmetric key you generated in step 1 with the Public key of the RSA key-pair, and give the recipient of the encrypted XML file, access to the Private key of the RSA key-pair as well as the encrypted symmetric key.
The recipient, then uses the RSA Private key to decrypt the symmetric key first, and then uses the "plaintext" symmetric key to decrypt the XML file.
What sabre150 was also attempting to explain to you, is the traditional way of transporting an encrypted "blob" that consists of data + symmetric key. With a modern key-management system, combining the two would be unnecessary.