Quantum Digital Signature: Difference between revisions

Digital Signatures (QDS) allow the exchange of classical messages from sender to multiple recipients, with a guarantee that the signature has come from a genuine sender. Additionally, it comes with the properties of [[Quantum Digital Signature#Properties|transferability]], [[Quantum Digital Signature#Properties|non-repudiation]] and [[Quantum Digital Signature#Properties|unforgeability]]. In contrast, classical digital signatures rely on authentication (taken as an assumption for some QDS protocols) i.e. the message has come from the claimed party; integrity i.e. the message has not been altered (if authentication is confirmed, this property is unforgeability) and non-repudiation (same as QDS). A digital signature not just authenticates an electronic document but also ensures that it has not been tampered with and prevents anyone denying a true signature.<br/>

Unlike classical digital signature schemes which generalize a two party model, QDS protocols always study a three party model as transferability is not inherent and has to be proved in the quantum case. Given this situation, usually, the third party acts as the judge (a verififer) who would gain nothing out of cheating, and hence, cheating strategy is only studied for seller (repudiation) and buyer (forgery). Quantum digital signatures provide unconditional security, not relying on any computational assumption which is its basic advantage over the classical schemes. However, over time classical unconditionally secure digital signature schemes have been realized. These classical protocols take extra some assumptions like trusted omnipotent (one who distributes everyone signatures) or authenticated message broadcast. QDS does not require any such assumption. Yet, the low key rate could render QDS impractical over classical digital signature schemes. At the same time, there exist post quantum secure Digital signature schemes based on hash-key cryptography which cannot be broken by quantum computers.  Still, if someone requires a lifetime security without the above mentioned assumptions, QDS is the answer. Areas to improve QDS could be addressing the key rate and scalability of key length with length of message.  

===Review Papers===