Secure Client- Server Delegated Computation

Functionality Description

Delegated Computation is the task of assigning computation on hidden data to a powerful untrusted party (a device) by a weak (in terms of computational powers) party while maintaining privacy of hidden data from the powerful party. Protocols under this functionality are commonly called Client-Server protocols. Delegated Quantum Computation (DQC) protocols involve partially or fully classical Client delegating a quantum computation to fully powerful single/multiple quantum Server/Servers. All DQC protocols involve three main stages, Preparation Stage, Computation Stage and Output Correction Stage. The roles of Client and Server in the different stages may differ according to the type of communication used see Protocols list.

Tags: Two Party, Universal Tasks,Secure Multiparty Delegated Computation, Quantum Enhanced Classical Delegated Computation

Use Case

• Quantum Task
• No classical analogue

Protocols

• The protocols enlisted here mainly differ in terms of the type of communication channels required. An online link means it is used throughout the protocol. An offline link means it is used only at the starting or ending of the protocol (one-time use channels) and there is no continuous exchange of information. A quantum communication link is used to transfer quantum states/information and classical links are used for exchange of classical information. These terms will be related with each protocol enlisted below.

1. Prepare and Send-Universal Blind Quantum Computation:Quantum Memory Network Stage. Requires classical online communication-quantum offline communication. Hides input, output and computation of the client
2. Measurement Only-Universal Blind Quantum Computation:Quantum Memory Network Stage. Requires classical online communication-quantum online communication. Hides input, output and computation of the client.
3. Pseudo-Secret Random Qubit Generator (PSQRG):Quantum Memory Network Stage. Requires classical offline communication- quantum offline communication.
4. Prepare and Send Quantum Fully Homomorphic Encryption:Quantum Memory Network Stage. Requires classical online communication-no quantum communication. Hides input and output of the client.
5. Classical Fully Homomorphic Encryption for Quantum Circuits:Quantum Memory Network Stage. Requires classical offline communication-no quantum communication. Hides input and output of the client.

• All the above protocols require the server to be a quantum memory network stage node. However, with respect to the client, (1) requires the client to only prepare and send quantum states while (2) requires client to just receive and measure quantum states. Thus, client belongs to a simple prepare and measure network stage node. This information is useful in case there are only a few nodes with advanced technologies like quantum memory.
• Protcols for verifiable version of protocols (1), (2), (4) can be found on the page Verifiable Delegated Quantum Computation. Verifiable versions of protocols (3) and (5) are open questions.

Properties

• Universality A protocol for delegated quantum computation is universal if it client can use the server to compute any quantum circuit.
• Correctness A protocol is correct if the output of client's input after Server's processing is correct, given that both parties follow the protocol honestly.
• Blindness The protocol is blind to the server (who, in this case is the adversary/dishonest party) means that client's computation is hidden from the server during the entire protocol.

Further Information

*contributed by Shraddha Singh