Threshold oblivious pseudorandom function in a key management system
A computing device is configured to divide an Oblivious Pseudorandom Function (OPRF) key to generate a plurality of N partial keys, distribute a respective one of the plurality of N partial keys to a corresponding plurality of N Key Management System (KMS) units. The computing device receives from a threshold number T of KMS units, a plurality T partial blinded keys, wherein the plurality T partial blinded keys are based on processing of a value of a blinded key received by a respective KMS unit and a corresponding stored partial key of the N partial keys, combines the plurality T of partial blinded keys into the blinded key, processes the blinded key based on the blinding key in accordance with an OPRF unblinding operation to generate a key and accesses secure information based on the key.
1. A computing device comprising:
an interface configured to interface and communicate with a communication system; memory that stores operational instructions; and
processing circuitry operably coupled to the interface and to the memory, wherein the processing circuitry is configured to execute the operational instructions to:
divide an Oblivious Pseudorandom Function (OPRF) key to generate a plurality of N partial keys;
distribute, via the communication system, a respective one of the plurality of N partial keys to a corresponding plurality of N Key Management System (KMS) units, the plurality of N partial keys distributed according to a distribution protocol for storage in the N KMS units;
receive, via the communication system and from a threshold number T of the KMS units, a plurality T of partial blinded keys, wherein the plurality T of partial blinded keys are based on processing of a value of a blinded key received by a respective KMS unit and a corresponding stored partial key of the N partial keys;
combine the plurality T of partial blinded keys into the blinded key;
process the blinded key based on the blinding key in accordance with an OPRF unblinding operation to generate a key; and
access secure information based on the key.
2. The computing device of claim 1 , wherein the distribution protocol includes generating the OPRF key at one location with the N partial keys computed and sent separately to one of the plurality of N KMS units.
3. The computing device of claim 1 , wherein the distribution protocol includes the plurality of N KMS units cooperating to derive the N partial keys of the OPRF key without the OPRF key existing in any single location.
4. The computing device of claim 1 , wherein the blinded key received by a respective KMS unit is included in a specific request to a threshold T number of distinct KMS units.
5. The computing device of claim 1 , wherein the blinded key received by a respective KMS unit is included as a single request to an intermediate layer, with the intermediate layer then selecting at least a threshold T number of KMS units to send a specific request to.
6. The computing device of claim 1 , wherein the computing device includes any of: a wireless smart phone, a cellular phone, a laptop, a personal digital assistant, a tablet, a personal computers (PC), a work station, a video game device, or another computing device including a Hardware Security Module (HSM).
7. The computing device of claim 1 , wherein the communication system includes at least one of a wireless communication system, a wire lined communication system, a nonpublic intranet system, a public internet system, a local area network (LAN), a wireless local area network (WLAN), a wide area network (WAN), a satellite communication system, a fiberoptic communication system, or a mobile communication system.
8. A method for secure processing, the method comprising:
dividing an Oblivious Pseudorandom Function (OPRF) key to generate a plurality of N partial keys;
distributing, via a communication system, a respective one of the plurality of N partial keys to a corresponding plurality of N Key Management System (KMS) units, the plurality of N partial keys distributed according to a distribution protocol for storage in the N KMS units;
receiving, via the communication system and from a threshold number T of the KMS units, a plurality T of partial blinded keys, wherein the plurality T of partial blinded keys are based on processing of a value of a blinded key received by a respective KMS unit and a corresponding stored partial key of the N partial keys;
combining the plurality T of partial blinded keys into the blinded key;
processing the blinded key based on the blinding key in accordance with an OPRF unblinding operation to generate a key; and
accessing secure information based on the key.
9. The method of claim 8 , wherein the distribution protocol includes generating the OPRF key at one location with the N partial keys computed and sent separately to one of the plurality of N KMS units.
10. The method of claim 8 , wherein the distribution protocol includes the plurality of N KMS units cooperating to derive the N partial keys of the OPRF key without the OPRF key existing in any single location.
11. The method of claim 8 , wherein the blinded key received by a respective KMS is included in a specific request to a threshold T number of distinct KMS units.
12. A system comprises:
an interface configured to interface and communicate with a communication system; memory that stores operational instructions; and
processing circuitry operably coupled to the interface and to the memory, wherein the processing circuitry is configured to execute the operational instructions to:
transmit, for installation, N distinct partial keys of an Oblivious Pseudorandom Function (OPRF) key to each of N distinct KMS units, using a distribution protocol;
transmit an Oblivious Key Access Request (OKAR) to at least a threshold number T of the N distinct KMS units;
perform a validation of the OKAR for at least a threshold number T of the N distinct KMS units;
for a validated OKAR:
receive an OKAR response from a corresponding one of the T number of the KMS units, the OKAR response using a root partial key combined with a blinded input to compute a blinded partial-key;
when at least a threshold number T of validated OKAR responses are received, combine the at least a threshold number T of validated OKAR responses to obtain a blinded OPRF output; and unblind the blinded OPRF output to recover an OPRF output to be used as a key; and
perform encryption or decryption operations with the key.
13. The system of claim 12 further comprising operational instructions to derive the N distinct partial keys based on a partial-key identifier.
14. The system of claim 13 , wherein the Oblivious Key Access Request (OKAR) includes one or more of:
a requester identifier;
a root key identifier;
a blinded input B where B=BlindingFunction(partial-key identifier);
authenticating information, or a challenge to the KMS unit.
15. The system of claim 14 , wherein the authenticating information includes one or more of:
credentials;
a password;
a token;
a response to a challenge;
a signature; or
a digital certificate.
16. The system of claim 15 , wherein the response to a challenge requires a KMS unit to prove its identity or correctness of operation.
17. The system of claim 15 , wherein the validation of the OKAR includes any of: ensuring credentials are correct for a requester identifier or ensuring a requester is authorized to access a key derived from a given root key identifier.
18. The system of claim 12 , wherein, when the validation indicates that a KMS unit is not authorized, receiving an error response from the KMS unit.
19. The system of claim 12 further comprises, when using an OPRF to derive a blinded partial-key reflects the KMS unit computing a blinded partial-key S, as S=OPRF(rootkey-partial, B).
20. The system of claim 12 further comprises, when a challenge is provided by a requester to the KMS unit, the KMS unit generating a response to the challenge and returning a response to the requester including the blinded partial-key and the challenge.