Two Variants Of Content Extraction Signatures

Tne notion of content extraction signatures,which was introduced by Steinfeld in 2001,is a special kind of digital signature.In the content extraction signature,the extracted signature holder can remove sensitive information from a signed message and extract a publicly verifiable extracted signature for a specified submessage,without any help from the signer of the original message.As a result,the content extraction signatures can be employed in many scenarios.However,the submessage may be signed and verified many times,it results in the long signatures or greatly increases computation costs.In practical applications,the extracted signature may be leaked by the verifier.Thus,the privacy of the user is at risk.In this thesis,several schemes are proposed to meet the needs in different demands.The main achievements of this thesis are concluded as follows:1.Motivated by the idea of batch signatures,two variants of content extraction signature schemes are presented based on commite vector and RSA,respectively.It retains all desirable properties of content extraction signature and efficiently improves the efficiency of the signing and verification.The study show that the proposed schemes are existentially unforgeable under chosen message attacks in the random oracle model.2.We integrate universal designated multi verifiers signatures and content extrac-tion signatures,and propose a new type of digital signature called universal designated multi verifier content extraction signature.It achieves all desirable properties of content extraction signature and efficiently resolves dissemination of extracted signature by verifiers at the same time.In the random oracle model,we prove that the scheme is secure under the assumption that the BDH problem is hard.At the end,the simulations were conducted to prove that our scheme is practical in the real world.