Non-malleable Randomness Encoders and Their Applications

  • Bhavana Kanukurthi
  • Sai Lakshmi Bhavana Obbattu
  • Sruthi Sekar
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10822)


Non-malleable Codes (NMCs), introduced by Dziembowski, Peitrzak and Wichs (ITCS 2010), serve the purpose of preventing “related tampering” of encoded messages. The most popular tampering model considered is the 2-split-state model where a codeword consists of 2 states, each of which can be tampered independently. While NMCs in the 2-split state model provide the strongest security guarantee, despite much research in the area we only know how to build them with poor rate (\(\varOmega (\frac{1}{logn})\), where n is the codeword length). However, in many applications of NMCs one only needs to be able to encode randomness i.e., security is not required to hold for arbitrary, adversarially chosen messages. For example, in applications of NMCs to tamper-resilient security, the messages that are encoded are typically randomly generated secret keys. To exploit this, in this work, we introduce the notion of “Non-malleable Randomness Encoders” (NMREs) as a relaxation of NMCs in the following sense: NMREs output a random message along with its corresponding non-malleable encoding.

Our main result is the construction of a 2-split state, rate-\(\frac{1}{2}\) NMRE. While NMREs are interesting in their own right and can be directly used in applications such as in the construction of tamper-resilient cryptographic primitives, we also show how to use them, in a black-box manner, to build a 3-split-state (standard) NMCs with rate \(\frac{1}{3}\). This improves both the number of states, as well as the rate, of existing constant-rate NMCs.



We thank Eshan Chattopadhyay for helpful discussions on connections between non-malleable codes and extractors. We also thank the reviewers of Eurocrypt for their useful comments.


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Copyright information

© International Association for Cryptologic Research 2018

Authors and Affiliations

  1. 1.Department of Computer Science and AutomationIndian Institute of ScienceBangaloreIndia
  2. 2.Department of MathematicsIndian Institute of ScienceBangaloreIndia

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