Today, someone who stores an encrypted file on a remote storage service cannot prove that the file was really deleted. Encryption stops the service from reading the file today, but it doesn't stop the service from secretly keeping a spare copy. If the decryption key later leaks, that spare becomes readable. In their paper “Semi-Quantum Cryptography with Certified Deletion,” Yael Tauman Kalai of MIT and Justin Raizes of NTT Research provide a method for a classical computer to use a quantum ser
