Application uses AES in CBC mode with 128 bit key. In this implementation key is always same and is equal to IV. Can attacker get the key or decrypt data? If he knows:
- First and second blocks of plaintexts;
- All blocks of ciphertexts.
The software mentioned above is malicious program, it encrypts all office files on user's computer. And I now attempt to help user get his data back. Reverse engineering of this program shows that key is unknown, but is always same and is equal to IV.