Let me be clear first and foremost: I do not think installing a backdoor in security algorithms is a good idea. They undermine the trust in the software and in the company that provides the service. That being said, I do agree that encryption provides a certain measure of protections for criminals and malicious actors against legitimate inquiries by authorities, which in turn can lead to dangerous situations.
I am also aware that cryptography is an INCREDIBLY complex subject matter, which should be left to the professionals with many years of experience. That said, in the below question, I will attempt to leave the creation of the cryptographic algorithm to the pros.
Now, the main question: Imagine a scheme like this:
- A new algorithm is developed with equal security as the current standards. In effect, the algorithm that replaces AES would be just as hard to crack as AES if you do not know the key.
- This algorithm generates one extra unique decryption key when used. This key is then sent via a secure channel (i.e. HTTPS or equivalent) to an NGO with the sole duty of guarding these keys. As soon as the tool gets confirmation that it is delivered, the tool securely deletes this key. The key is always different and strong enough that brute-forcing is not feasible. In addition, the encryption software will require a usable connection to the NGO via internet when the encryption is started to ensure that the key can be sent.
- Once the key arrives, it is stored in an offline, airgapped database that can only be accessed in a single room with rigourous safety. In addition, the database and the machine it is located have tamper protection, similar to tamper protection on bank transports: any access that's out of the ordinary, like too many requests within a certain period or too many faulty requests, and the machine gets wiped.
- When a legitimate law enforcement organization has need of a key to decrypt, it sends a formal request to the NGO. The NGO first analyzes the request based on the importance of the request. the NGO allows decryption when the suspect is strongly incriminated by other evidence, and only in the case of terrorism, murder or abuse of a minor (which are probably the only widely accepted reasons for public opinion).
- If the NGO allows decryption, a trusted employee of the NGO goes to the room the database is accessible from and downloads the key on a read-only medium with similar tamper protection as the database. This medium is then handed over to the law enforcement organization that originally requested it. At this point, normal law enforcement will take over.
Assuming all of the above is feasible, what problems can arise from this system?