如果数据已知，则检索加密密钥

Question

Is there any possible way or attack to retrieve the key from encrypted data if a part of the original data is known? Also if a file is compressed and then encrypted, does the compression headers give away any clue to find the key since popular compression format headers are well known?

Answer 1

Recovering the key is not possible with a strong encryption system. If you know some of the original data, the plaintext, then the attack is called a "known plaintext attack". Strong cyphers are proof against such attacks.

The known header to a compressed file is just another form of known plaintext attack.