How to decrypt encrypted files in an Android malware

Описание: This is a demo video, presented at RSA Conference Europe, in October 2011. It is meant to help reverse engineer deal with mobile malware that use encryption.

Android/DrdLight uses DES encryption to encrypt one of its configuration file, prefer.dat.
We show how easy (or not?) it is to decrypt the file, using Dalvik and Java decompilers. We spot the encryption key and encryption method, and copy / paste this in our own decryption code.