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Prepare and Measure Quantum Digital Signature: Difference between revisions
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Prepare and Measure Quantum Digital Signature (edit)
Revision as of 15:13, 3 June 2019
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Distribution phase can be divided into the following steps: | Distribution phase can be divided into the following steps: | ||
*''' Key Distribution:''' Seller generates her (public key, private key) pair and shares the public key with both receivers in this step. For each possible message (0 or 1), she generates two identical sequences/copies (one for each receiver per possible message) of randomly chosen BB84 ∈ {0,1,+,−} states. The sequence of states is called quantum public key and its classical description, private key. She then sends copies of each quantum public key to the receivers while keeping both the private keys secret to herself. At the end of this step, the seller has two private keys, one for each possible message. Similarly, each receiver has two quantum public keys, one for each possible message. | *''' Key Distribution:''' Seller generates her (public key, private key) pair and shares the public key with both receivers in this step. For each possible message (0 or 1), she generates two identical sequences/copies (one for each receiver per possible message) of randomly chosen BB84 ∈ {0,1,+,−} states. The sequence of states is called quantum public key and its classical description, private key. She then sends copies of each quantum public key to the receivers while keeping both the private keys secret to herself. At the end of this step, the seller has two private keys, one for each possible message. Similarly, each receiver has two quantum public keys, one for each possible message. | ||
*''' State Elimination:''' Receivers store their classical records of the quantum public keys in this step. For each quantum public key received, a receiver randomly chooses X or Z basis for each qubit and measures. Whatever outcome he gets, the receiver is certain that seller could not have generated a state orthogonal to his outcome. So, he records the state orthogonal to his outcome as the eliminated signature element. Such measurement is called ’Quantum State Elimination’. The sequence thus generated by measurement of all the qubits in a public key is called receiver’s eliminated signature for the respective quantum public key. Thus, each receiver finally has two eliminated signatures, one for each possible message. | *''' State Elimination:''' Receivers store their classical records of the quantum public keys in this step. For each quantum public key received, a receiver randomly chooses pauli X or Z basis for each qubit and measures. Whatever outcome he gets, the receiver is certain that seller could not have generated a state orthogonal to his outcome. So, he records the state orthogonal to his outcome as the eliminated signature element. Such measurement is called ’Quantum State Elimination’. The sequence thus generated by measurement of all the qubits in a public key is called receiver’s eliminated signature for the respective quantum public key. Thus, each receiver finally has two eliminated signatures, one for each possible message. | ||
*'''Symmetrisation:''' The two receivers exchange half of their randomly chosen eliminated signature elements. This prevents a dishonest seller to succeed in cheating by sending dissimilar public keys to the receivers. Thus ends the distribution phase. | *'''Symmetrisation:''' The two receivers exchange half of their randomly chosen eliminated signature elements. This prevents a dishonest seller to succeed in cheating by sending dissimilar public keys to the receivers. Thus ends the distribution phase. | ||