Patent ID: 8620879

Claim:
A computer implemented method for storing files on a cloud-based server, the method comprising: receiving, at the cloud-based server, from a client computer controlled by the user, a hash value for a file; determining, through at least one processor of the cloud-based server, whether a file with a hash value identical to the received hash value is already stored on the cloud-based server; if a file with a hash value identical to the received hash value is already stored on the cloud-based server, further: challenging the user's right to access the copy of the file that is stored on the cloud-based server; receiving the user's response to the challenge; determining whether the user has the right to access the copy of the file that is stored on the cloud-based server based on the user's response to the challenge; and granting the user the right to access the copy of the file that is stored on the cloud-based server when the user successfully responds to the challenge.