Method for proving retrievability of information

1. A method for proving retrievability of information, the method being performed in a memory available to one or more computation devices, wherein credentials between a user device, a storing device and an auditing device between each pair of the devices are exchanged and used for communication between them, the method comprising:

a) encoding, by the user device or the auditing device, information to be stored on the storing device;

b) storing the encoded information on the storing device;

c) verifying that the stored information was stored correctly on the storage device by the auditing device using unpredictable random information;

d) transmitting correctness information to the user device, the correctness information being secure and being generated based on the result of the verification by the auditing device; and

e) validating the correctness information by the user device for proving retrievability of the stored information and the unpredictable random information,

wherein a source for unpredictable random information is based on Bitcoin and is commonly used by the user device and the auditing device.

2. The method according to claim 1 , wherein the auditing device is provided with contract information by the user device, wherein the contract information specifies a checking policy for the auditing device and/or the information to be proved for retrievability.

3. The method according to claim 1 , wherein the stored information is different from the information to be stored, wherein the information to be stored is recoverable from the stored information.

4. The method according to claim 1 , wherein an information dispersal algorithm is applied to the information to be stored prior to storing.

5. The method according to claim 1 , wherein the correctness information is based on information of an external mutually trusted entity.

6. The method according to claim 1 , wherein the correctness information is provided as a log-file by the auditing device.

7. The method according to claim 1 , wherein step c) and/or step e) is based on a proof-of retrievability protocol.

8. The method according to claim 1 , wherein the auditing device performs a proof-of-retrievability protocol with the storing device, and wherein the user device audits the auditing device using a proof-of-retrievability protocol.

9. The method according to claim 2 , wherein the contract information includes at least one of the following: maximum interval within which the auditing device notifies the user device of an at least partial loss of said stored information and maximum failure tolerance.

10. A system for proving retrievability (POR) of information, the system comprising:

a user device,

a storing device, and

an auditing device, wherein credentials between the user device, the storing device and the auditing device between each pair of the devices are exchanged and used for communication between them,

wherein at least one of the user device or the auditing device is configured to encode the information to be stored on the storing device,

wherein the user device is configured to validate correctness information for proving retrievability of the stored information using unpredictable random information,

wherein the storing device is configured to store the encoded information,

wherein the auditing device is configured to verify that the stored information was stored correctly on the storage device using the unpredictable random information, and to transmit correctness information to the user device, the correctness information being secure and being generated based on the result of the verification by the auditing device,

wherein a source for unpredictable random information is based on Bitcoin and is commonly used by the user device and the auditing device.

11. A method for proving retrievability of information, the method being performed in a memory available to one or more computation devices, wherein credentials between a user device, a storing device and an auditing device between each pair of the devices are exchanged and used for communication between them, the method comprising:

a) encoding, by the user device or the auditing device, information to be stored on the storing device;

b) storing the encoded information on the storing device;

c) verifying that the stored information was stored correctly on the storage device by the auditing device using unpredictable random information;

d) transmitting correctness information to the user device, the correctness information being secure and being generated based on the result of the verification by the auditing device; and

e) validating the correctness information by the user device for proving retrievability of the stored information and the unpredictable random information,

wherein the auditing device is provided with contract information by the user device, wherein the contract information specifies a checking policy for the auditing device and/or the information to be proved for retrievability; and

wherein the contract information includes at least one of the following: maximum interval within which the auditing device notifies the user device of an at least partial loss of said stored information and maximum failure tolerance.