Four-factor authentication

A non-transitory computer-readable storage medium storing a computer program to verify that a user is using a device at a pre-specified location between a start time and an end time, the computer program comprising executable instructions that cause a computer to:

• calculate a challenge and an answer that is a function of the challenge;
• generate and store in a blockchain, a commitment including an identity of the user, an identity of the device, the pre-specified location associated with the user, the start time of usage of the device, the end time of usage of the device, and the calculated challenge;
• generate a visual code of the device to carry the answer;
• encrypt the generated visual code with a public key of the device, wherein the encrypted visual code may only be decrypted with a private key of the device;
• and
• store the encrypted visual code in the blockchain.

A system for verifying that a user is using a device at a pre-specified location between a start time and an end time, the system comprising:

• a blockchain;
• a device to be authenticated, wherein the device accesses the blockchain through a network connection,
• wherein the blockchain stores a commitment including an identity of the device to authenticate, an identity of a user of the device, a pre-specified location associated with the user, the start time of usage of the device, the end time of usage of the device, and a challenge;
• a public key and a private key of the device for encryption and decryption that are stored in the device and in the blockchain;
• a public key and a private key of the user for encryption and decryption that are stored in the blockchain;
• and
• a scheduler to generate a visual code of the device to carry an answer to the challenge, to encrypt the generated visual code with the public key of the device, wherein the encrypted visual code may only be decrypted with a private key of the device, and to store the encrypted visual code in the blockchain.