zip file can be find here http://www.cs.sjsu.edu/~stamp/infosec/files/

5. Obtain the file encrypted.zip from the textbook website and extract the file encrypted, jar. This application was encrypted using Sand- Mark [63], with the "obfuscate" tab and "Class Encryptor" option selected and, possibly, other obfuscation options.

a. Generate a decompiled version of this program directly from the obfuscated (and encrypted) code. Hint: Do not attempt to use a cryptanalytic attack to break the encryption. Instead, look for an unencrypted class file. This is a custom class loader that decrypts the encrypted files before they are executed. Reverse this custom class loader and modify it so that it prints out the class files in plaintext.

b. How could you make this encryption scheme more difficult to break?