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Quotable Signatures for Authenticating Shared Quotes

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Part of the Lecture Notes in Computer Science book series (LNCS,volume 14168)


Quotable signature schemes are digital signature schemes with the additional property that from the signature for a message, any party can extract signatures for (allowable) quotes from the message, without knowing the secret key or interacting with the signer of the original message. Crucially, the extracted signatures are still signed with the original secret key. We define a notion of security for quotable signature schemes and construct a concrete example of a quotable signature scheme, using Merkle trees and classical digital signature schemes. The scheme is shown to be secure, with respect to the aforementioned notion of security. Additionally, we prove bounds on the complexity of the constructed scheme. Finally, concrete use cases of quotable signatures are considered, using them to combat misinformation by bolstering authentic content on social media. We consider both how quotable signatures can be used, and why using them could help mitigate the effects of fake news.


  • quotable signatures
  • digital signatures
  • Merkle trees
  • authenticity
  • fake news

The first and third authors were supported in part by the Independent Research Fund Denmark, Natural Sciences, grant DFF-0135-00018B. All authors are currently associated with DDC – the Digital Democracy Center at the University of Southern Denmark.

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    Specifically, we talked with the editor in charge of the platforms and the editor in charge of the digital editorial office at a large media company that produces multiple newspapers for different regional areas, in both paper and digital versions.

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Correspondence to Kim S. Larsen .

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Boyar, J., Erfurth, S., Larsen, K.S., Niederhagen, R. (2023). Quotable Signatures for Authenticating Shared Quotes. In: Aly, A., Tibouchi, M. (eds) Progress in Cryptology – LATINCRYPT 2023. LATINCRYPT 2023. Lecture Notes in Computer Science, vol 14168. Springer, Cham.

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