I have used TrueCrypt but it uses a cascaded encryption. I want to know about encrypting a file using two ciphers with each cipher having different key.
Cipher A (Block Cipher) - with Key KA
Cipher B (Stream Cipher) - with Key KB
First I am encrypting a file with Cipher A (KA). Again I am encrypting a file using Cipher B (KB).
Does this, in any way, make the final encrypted file vulnerable? Or, rather, leave some loopholes.
One other approach I thought is to compress a file before applying second cipher so as to make it more random.
Cipher A -> ZIP -> Cipher B
How secure is this and in which mode the two ciphers be operated to achieve high security?
** Edited **
Both the keys are different. Encrypted file also does not contain any key.