Cryptanalysis of FIDES

  • Itai Dinur
  • Jérémy JeanEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8540)


FIDES is a lightweight authenticated cipher, presented at CHES 2013. The cipher has two version, providing either 80-bit or 96-bit security. In this paper, we describe internal state-recovery attacks on both versions of FIDES, and show that once we recover the internal state, we can use it to immediately forge any message. Our attacks are based on a guess-and-determine algorithm, exploiting the slow diffusion of the internal linear transformation of FIDES. The attacks have time complexities of \(2^{75}\) and \(2^{90}\) for FIDES-80 and FIDES-96, respectively, use a very small amount of memory, and their most distinctive feature is their very low data complexity: the attacks require at most 24 bytes of an arbitrary plaintext and its corresponding ciphertext, in order to break the cipher with probability 1.


Authenticated encryption FIDES Cryptanalysis Guess-and-determine 


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Copyright information

© International Association for Cryptologic Research 2015

Authors and Affiliations

  1. 1.École Normale SupérieureParisFrance
  2. 2.Nanyang Technological UniversitySingaporeSingapore

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