When the police want data from tech companies, the people being investigated often have no clue that their data are being searched. That’s why MIT has created a cryptography-based systems that could help track data requests while still protecting investigations, police, and those who are under investigation. The system would require law enforcers to submit requests to a public ledger sometime after the fact using a “cryptographic commitment.” The approach would ensure that police and courts send all the right documents in a way the public can see, but would keep the agencies' actions confidential.