Annual International Conference on the Theory and Applications of Cryptographic Techniques

EUROCRYPT 2010: Advances in Cryptology – EUROCRYPT 2010 pp 92-112

Secure Obfuscation for Encrypted Signatures

  • Satoshi Hada
Conference paper

DOI: 10.1007/978-3-642-13190-5_5

Volume 6110 of the book series Lecture Notes in Computer Science (LNCS)
Cite this paper as:
Hada S. (2010) Secure Obfuscation for Encrypted Signatures. In: Gilbert H. (eds) Advances in Cryptology – EUROCRYPT 2010. EUROCRYPT 2010. Lecture Notes in Computer Science, vol 6110. Springer, Berlin, Heidelberg


Obfuscation is one of the most intriguing open problems in cryptography and only a few positive results are known. In TCC’07, Hohenberger et al. proposed an obfuscator for a re-encryption functionality, which takes a ciphertext for a message encrypted under Alice’s public key and transforms it into a ciphertext for the same message under Bob’s public key [24]. It is the first complicated cryptographic functionality that can be securely obfuscated, but obfuscators for such cryptographic functionalities are still elusive. In this paper, we consider obfuscation for encrypted signature (ES) functionalities, which generate a signature on a given message under Alice’s secret signing key and encrypt the signature under Bob’s public encryption key. We propose a special ES functionality, which is the sequential composition of Waters’s signature scheme [33] and the linear encryption scheme proposed by Boneh, Boyen, and Shacham [5], and construct a secure obfuscator for it. We follow the security argument by Hohenberger et al. to prove that our proposed obfuscator satisfies a virtual black-box property (VBP), which guarantees that the security of the signature scheme is preserved even when adversaries are given an obfuscated program. Our security argument is in the standard model.


Obfuscationencrypted signaturessigncryptionbilinear map
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Copyright information

© Springer-Verlag Berlin Heidelberg 2010

Authors and Affiliations

  • Satoshi Hada
    • 1
  1. 1.IBM ResearchTokyo