Verifiably Encrypted Signatures with Short Keys Based on the Decisional Linear Problem and Obfuscation for Encrypted VES

  • Ryo Nishimaki
  • Keita Xagawa
Conference paper

DOI: 10.1007/978-3-642-36362-7_25

Part of the Lecture Notes in Computer Science book series (LNCS, volume 7778)
Cite this paper as:
Nishimaki R., Xagawa K. (2013) Verifiably Encrypted Signatures with Short Keys Based on the Decisional Linear Problem and Obfuscation for Encrypted VES. In: Kurosawa K., Hanaoka G. (eds) Public-Key Cryptography – PKC 2013. Lecture Notes in Computer Science, vol 7778. Springer, Berlin, Heidelberg

Abstract

Verifiably encrypted signatures (VES) are signatures encrypted by a public key of a trusted third party and we can verify their validity without decryption. This paper proposes a new VES scheme which is secure under the decisional linear (DLIN) assumption in the standard model. We also propose new obfuscators for encrypted signatures (ES) and encrypted VES (EVES) which are secure under the DLIN assumption.

All previous efficient VES schemes in the standard model are either secure under standard assumptions (such as the computational Diffie-Hellman assumption) with large verification (or secret) keys or secure under (non-standard) dynamic q-type assumptions (such as the q-strong Diffie-Hellman extraction assumption) with short verification keys. Our construction is the first efficient VES scheme with short verification (and secret) keys secure under a standard assumption (DLIN).

As by-products of our VES scheme, we construct new obfuscators for ES/EVES based on our new VES scheme. They are more efficient than previous obfuscators with respect to the public key size. Previous obfuscators for EVES are secure under non-standard assumption and use zero-knowledge (ZK) proof systems and Fiat-Shamir heuristics to obtain non-interactive ZK, i.e., its security is considered in the random oracle model. Thus, our construction also has an advantage with respect to assumptions and security models. Our new obfuscator for ES is obtained from our new obfuscator for EVES.

Keywords

verifiably encrypted signature obfuscation encrypted verifiably encrypted signature decisional linear assumption 

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Copyright information

© International Association for Cryptologic Research 2013

Authors and Affiliations

  • Ryo Nishimaki
    • 1
  • Keita Xagawa
    • 1
  1. 1.NTT Secure Platform LaboratoriesMusashino-shiJapan

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