Original: Nonetheless poor cipher usage or reliance on home-grown proprietary algorithms that have not been subject to thorough scrutiny has resulted in many computer-age encryption systems that are still subject to ciphertext-only attack.
Simplified: On the other hand poor cipher depends on home-grown proprietary algorithms that have not been subjected to extensive testing and inspection; for this reason many computer-age encryption systems are still subject to ciphertext-only attack but still in use.