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Arbitrated Quantum Digital Signature: Difference between revisions
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Like other QDS protocols, it is divided into two phases: Distribution (Key Generation) and Messaging (Signing and Verification). This scheme is presented between seller (one who signs the message), buyer (one whom the signed message is sent) and PKG (generates and distributes public-private key for seller) and a buyer.</br> | Like other QDS protocols, it is divided into two phases: Distribution (Key Generation) and Messaging (Signing and Verification). This scheme is presented between seller (one who signs the message), buyer (one whom the signed message is sent) and PKG (generates and distributes public-private key for seller) and a buyer.</br> | ||
* '''Key Generation''': In this step, PKG generates derives the public key of the seller and generates a private key which is secretly sent to Seller over insecure classical channel. Seller's public key is derived from her personal information such as her email-id over a public channel. A | * '''Key Generation''': In this step, PKG generates derives the public key of the seller and generates a private key which is secretly sent to Seller over insecure classical channel. Seller's public key is derived from her personal information such as her email-id over a public channel. A one way function is chosen by PKG randomly and secretly (known as master key), which uses the classical public key as its input. A random OTP of the same length as the function outcome (random key), is used to convert it (the outcome) into seller's private key by performing bit-wise modulo 2 sum (exclusive OR gate). The quantum pre-shared common key (assumption) is then used to one-time pad the private key via [[Arbitrated Quantum Digital Signature#References|Quantum Vernam Cipher (1), (2)]]. The one-time padded cipher-text was communicated to seller (over insecure channel). Seller un-pads the cipher-text to obtain the private key using the pre-shared common key. Hence, in the end, everyone knows seller's public key and, only PKG and seller know her private key. | ||
* '''Signing''': In this step, the | * '''Signing''': In this step, the seller generates a signature quantum state using the message she wants to send, her public key and private key. The seller selects a quantum one way function publicly to generate a quantum digest (directory) using these classical inputs. | ||
** The Signer selects two random strings and generates a quantum state of the message using these random strings. | ** The Signer selects two random strings and generates a quantum state of the message using these random strings. | ||
** The public and the private key are used to generate the signature quantum state from the state produced in the previous step. | ** The public and the private key are used to generate the signature quantum state from the state produced in the previous step. | ||