Patent ID: 8621240

Claim:
A method for protecting backup data from unauthorized access on a backup server that implements a hash file system for storing backup data in content addressed storage, the method comprising: receiving, at a backup server, a hash value from a client, the hash value identifying a location of data of the client that is stored in the content addressed storage, wherein the hash value is obtained by hashing at least one of the data itself and other data associated with the data; encrypting at least a portion of the hash value using an encryption key that is specific to the client to generate an encrypted hash value, wherein the hash value is used to eliminate redundant data from the backup data and to point to the data stored in the content addressed storage and identified by the hash value, wherein the encrypted hash value protects the data from being accessed by other clients that are not associated with the encryption key that is specific to the client; and providing the encrypted hash value to the client, wherein the client stores the encrypted hash value for later use in communicating with the backup server regarding the data of the client identified by the encrypted hash value, wherein the encrypted hash value encrypted with the encryption key specific to the client prevents a second client from accessing the backup data associated with the client, wherein the backup server enables access to the client's data only if the encrypted hash value is successfully decrypted using the decryption key specific to the client, wherein a decryption key specific to the second client fails to successfully decrypt the encrypted hash value which enables the backup server to protect the client's data from unauthorized access by the second client.