Multi-key Analysis of Tweakable Even-Mansour

نویسندگان

  • Zhiyuan Guo
  • Wenling Wu
  • Renzhang Liu
  • Liting Zhang
چکیده

The tweakable Even-Mansour construction generalizes the conventional Even-Mansour scheme through replacing round keys by strings derived from a master key and a tweak. Besides providing plenty of inherent variability, such a design builds a tweakable block cipher from some lower level primitive. In the present paper, we evaluate the multi-key security of TEM-1, one of the most commonly used one-round tweakable Even-Mansour schemes (formally introduced at CRYPTO 2015), which is constructed from a single n-bit permutation P and a function f(k, t) linear in k from some tweak space to {0, 1}. Based on giant component theorem in random graph theory, we propose a collision-based multi-key attack on TEM-1 in the known-plaintext setting. Furthermore, inspired by the methodology of Fouque et al. presented at ASIACRYPT 2014, we devise a novel way of detecting collisions and eventually obtain a memory-efficient multi-key attack in the adaptive chosen-plaintext setting. As important applications, we utilize our techniques to analyze the authenticated encryption algorithms Minalpher (a second-round candidate of CAESAR) and OPP (proposed at EUROCRYPT 2016) in the multi-key setting. We describe knownplaintext attacks on Minalpher and OPP without nonce misuse, which enable us to recover almost all O(2n/3) independent masks by making O(2n/3) queries per key and costing O(22n/3) memory overall. After defining appropriate iterated functions and accordingly changing the mode of creating chains, we improve the basic blockwiseadaptive chosen-plaintext attack to make it also applicable for the nonce-respecting setting. While our attacks do not contradict the security proofs of Minalpher and OPP in the classical setting, nor pose an immediate threat to their uses, our results demonstrate their security margins in the multi-user setting should be carefully considered. We emphasize this is the very first third-party analysis on Minalpher and OPP.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

On the Provable Security of the Tweakable Even-Mansour Cipher Against Multi-Key and Related-Key Attacks

Cogliati et al. introduced the tweakable Even-Mansour cipher constructed from a single permutation and an almost-XORuniversal (AXU) family of hash functions with tweak and key schedule. Most of previous papers considered the security of the (iterated) tweakable Even-Mansour cipher in the single-key setting. In this paper, we focus on the security of the tweakable Even-Mansour cipher in the mult...

متن کامل

Connecting tweakable and multi-key blockcipher security

The significance of understanding blockcipher security in the multi-key setting is highlighted by the extensive literature on attacks, and how effective key size can be significantly reduced. Nevertheless, little attention has been paid in formally understanding the design of multi-key secure blockciphers. In this work, we formalize the multi-key security of tweakable blockciphers in case of ge...

متن کامل

Beyond-Birthday-Bound Security for Tweakable Even-Mansour Ciphers with Linear Tweak and Key Mixing

The iterated Even-Mansour construction defines a block cipher from a tuple of public n-bit permutations (P1, . . . , Pr) by alternatively xoring some n-bit round key ki, i = 0, . . . , r, and applying permutation Pi to the state. The tweakable Even-Mansour construction generalizes the conventional Even-Mansour construction by replacing the n-bit round keys by n-bit strings derived from a master...

متن کامل

XPX: Generalized Tweakable Even-Mansour with Improved Security Guarantees

We present XPX, a tweakable blockcipher based on a single permutation P . On input of a tweak (t11, t12, t21, t22) ∈ T and a message m, it outputs ciphertext c = P (m⊕∆1)⊕∆2, where ∆1 = t11k⊕t12P (k) and ∆2 = t21k⊕t22P (k). Here, the tweak space T is required to satisfy a certain set of trivial conditions (such as (0, 0, 0, 0) 6∈ T ). We prove that XPX with any such tweak space is a strong twea...

متن کامل

Tweaking Even-Mansour Ciphers

We study how to construct efficient tweakable block ciphers in the Random Permutation model, where all parties have access to public random permutation oracles. We propose a construction that combines, more efficiently than by mere black-box composition, the CLRW construction (which turns a traditional block cipher into a tweakable block cipher) of Landecker et al. (CRYPTO 2012) and the iterate...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2016