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Arbitrated Quantum Digital Signature: Difference between revisions
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** The public and the private key are used to perform Hadamard transformation on the state produced in the previous step in order to generate the signature quantum state. | ** The public and the private key are used to perform Hadamard transformation on the state produced in the previous step in order to generate the signature quantum state. | ||
** The Seller then performs some operation using her private key and measures the quantum state. It can be shown the states were on of the BB84 states and hence, can have one of the two possible bases ([[Glossary#Quantum States|X basis,Z basis or + basis,x basis]]) and four possible states. She records the basis and classical bit representing the state obtained. | ** The Seller then performs some operation using her private key and measures the quantum state. It can be shown the states were on of the BB84 states and hence, can have one of the two possible bases ([[Glossary#Quantum States|X basis,Z basis or + basis,x basis]]) and four possible states. She records the basis and classical bit representing the state obtained. | ||
**Seller then concatenates these classical bits, the two random string bits, and a timestamp unique to the signature. The concatenated classical string is used as the input of publicly chosen QOWF. | **Seller then concatenates these classical bits, the two random string bits, and a timestamp unique to the signature. The concatenated classical string is used as the input of publicly chosen QOWF, to get the output called 'quantum digest'. She produces some copies of quantum digest depending on the number of recipients. | ||
**Seller then encrypts the timestamp and quantum output of QOWF with pre-shared common key via quantum vernam cipher. PKG unpads these and publicly announces for buyer's verification step. | **Seller then encrypts the timestamp and quantum output of QOWF with pre-shared common key via quantum vernam cipher. PKG unpads these and publicly announces for buyer's verification step. | ||
** Sellers sends the signature to the buyer which includes the signature quantum state, message, timestamp and basis states. | ** Sellers sends the signature to the buyer which includes the signature quantum state, message, timestamp and basis states. | ||
* '''Verification''': In this method, the verifier checks the authenticity of the signature. | * '''Verification''': In this method, the verifier checks the authenticity of the signature (whether the message has coe from a genuine seller). | ||
** The | ** The verifier performs some quantum gates using seller's public key and message on the signature quantum state. | ||
** | |||
** One of the randomly selected string by the Signer can be easily inferred by the Verifier from the state after the measurement. The Verifier is then able to generate their own copy of quantum digital digest using the publicly announced quantum one way function. | ** One of the randomly selected string by the Signer can be easily inferred by the Verifier from the state after the measurement. The Verifier is then able to generate their own copy of quantum digital digest using the publicly announced quantum one way function. | ||
** Verifier now publicly gains the timestamp and quantum digital digest from PKG and verifies that state with the produced quantum digital digest in the above step with the SWAP test. As the SWAP test has a probabilistic result, it is performed several times with the copies of quantum digital digest and then verified. | ** Verifier now publicly gains the timestamp and quantum digital digest from PKG and verifies that state with the produced quantum digital digest in the above step with the SWAP test. As the SWAP test has a probabilistic result, it is performed several times with the copies of quantum digital digest and then verified. | ||