Cryptology ePrint Archive: Report 2013/683

Separations in Circular Security for Arbitrary Length Key Cycles

Venkata Koppula and Kim Ramchen and Brent Waters

Abstract: While standard notions of security suffice to protect any message supplied by an adversary, in some situations stronger notions of security are required. One such notion is n-circular security, where ciphertexts Enc(pk1, sk2), Enc(pk2, sk3), ..., Enc(pkn, sk1) should be indistinguishable from encryptions of zero.

In this work we prove the following results for n-circular security:

- For any n there exists an encryption scheme that is IND-CPA secure but not n-circular secure.

- There exists a bit encryption scheme that is IND-CPA secure, but not 1-circular secure.

- If there exists an encryption system where an attacker can distinguish a key encryption cycle from an encryption of zeroes, then in a transformed cryptosystem there exists an attacker which recovers secret keys from the encryption cycles.

Our first two results apply a novel utilization of indistinguishability obfuscation. The last result is generic and applies to any such cryptosystem.

Category / Keywords:

Date: received 23 Oct 2013

Contact author: kramchen at cs utexas edu

Available format(s): PDF | BibTeX Citation

Version: 20131024:092858 (All versions of this report)

Discussion forum: Show discussion | Start new discussion


[ Cryptology ePrint archive ]