Cryptology ePrint Archive: Report 2015/813

Revisiting Turning Online Cipher Off

Ritam Bhaumik and Mridul Nandi

Abstract: In 'Turning Online Ciphers Off', a class of constructions was defined based on layers of secure online ciphers interleaved with simple mixing layers (like reversing and block-shifting). Here we show that an SPRP construction proposed in the work cited is insecure. Howevewr, the same construction is secure under the assumption that the underlying construction is online-but-last ciphers. We include a simpler proof for beyond-birthday security of other constructions proposed in the same work.

Category / Keywords: secret-key cryptography / symmetric-key cryptography, cryptanalysis, SPRP security, provable security, online, online ciphers

Date: received 15 Aug 2015

Contact author: bhaumik ritam at gmail com

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Version: 20150817:160955 (All versions of this report)

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