Abstract. At CHES 2010, the new block cipher PRINTcipher was presented as a light-weight encryption solution for printable circuits [15]. The best attack to date is a differential attack [1] that breaks less than half of the rounds. In this paper, we will present a new attack called invariant subspace attack that breaks the full cipher for a significant fraction of its keys. This attack can be seen as a weak-key variant of a statistical saturation attack. For such weak keys, a chosen plaintext distinguishing attack can be mounted in unit time. In addition to breaking PRINTcipher, the new attack also gives us new insights into other, more well-established attacks. We derive a truncated differential characteristic with a round-independent but highly key-dependent probability. In addition, we also show that for weak keys, strongly biased linear approximations exists for any number of rounds. In this sense, PRINTcipher behaves very differently to what is usually -often implicitly -assumed.

Abstract. As two important cryptanalytic methods, impossible differential cryptanalysis and integral cryptanalysis have attracted much attention in recent years. Although relations among other important cryptanalytic approaches have been investigated, the link between these two methods has been missing. The motivation in this paper is to fix this gap and establish links between impossible differential cryptanalysis and integral cryptanalysis.Firstly, by introducing the concept of structure and dual structure, we prove that a → b is an impossible differential of a structure E if and only if it is a zero correlation linear hull of the dual structure E ⊥ . More specifically, constructing a zero correlation linear hull of a Feistel structure with SP -type round function where P is invertible, is equivalent to constructing an impossible differential of the same structure with P T instead of P . Constructing a zero correlation linear hull of an SPN structure is equivalent to constructing an impossible differential of the same structure with (P −1 ) T instead of P . Meanwhile, our proof shows that the automatic search tool presented by Wu and Wang could find all impossible differentials of both Feistel structures with SP -type round functions and SPN structures, which is useful in provable security of block ciphers against impossible differential cryptanalysis.Secondly, by establishing some boolean equations, we show that a zero correlation linear hull always indicates the existence of an integral distinguisher while a special integral implies the existence of a zero correlation linear hull. With this observation we improve the integral distinguishers of Feistel structures by 1 round, build a 24-round integral distinguisher of CAST-256 based on which we propose the best known key recovery attack on reduced round CAST-256 in the non-weak key model, present a 12-round integral distinguisher of SMS4 and an 8-round integral distinguisher of Camellia without F L/F L −1 . Moreover, this result provides a novel way for establishing integral distinguishers and converting known plaintext attacks to chosen plaintext attacks.Finally, we conclude that an r-round impossible differential of E always leads to an r-round integral distinguisher of the dual structure E ⊥ . In the case that E and E ⊥ are linearly equivalent, we derive a direct link between impossible differentials and integral distinguishers of E . Specifically, we obtain that an r-round impossible differential of an SPN structure, which adopts a bit permutation as its linear layer, always indicates the existence of an r-round integral distinguisher. Based on this newly established link, we deduce that impossible differentials of SNAKE(2), PRESENT, PRINCE and ARIA, which are independent of the choices of the S-boxes, always imply the existence of integral distinguishers.Our results could help to classify different cryptanalytic tools. Furthermore, when designing a block cipher, the designers need to demonstrate that the cipher has sufficient security margins against impo...

Abstract. In this paper we analyse two variants of SIMON family of light-weight block ciphers against linear cryptanalysis and present the best linear cryptanalytic results on these variants of reduced-round SIMON to date.We propose a time-memory trade-off method that finds differential/linear trails for any permutation allowing low Hamming weight differential/linear trails. Our method combines low Hamming weight trails found by the correlation matrix representing the target permutation with heavy Hamming weight trails found using a Mixed Integer Programming model representing the target differential/linear trail. Our method enables us to find a 17-round linear approximation for SIMON-48 which is the best current linear approximation for SIMON-48. Using only the correlation matrix method, we are able to find a 14-round linear approximation for SIMON-32 which is also the current best linear approximation for SIMON-32.The presented linear approximations allow us to mount a 23-round key recovery attack on SIMON-32 and a 24-round Key recovery attack on SIMON-48/96 which are the current best results on SIMON-32 and SIMON-48. In addition we have an attack on 24 rounds of SIMON-32 with marginal complexity.

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Physical unclonable functions (PUF) are cryptographic primitives employed to generate true and intrinsic randomness which is critical for cryptographic and secure applications. Thus, the PUF output (response) has properties that can be utilized in building a true random number generator (TRNG) for security applications. The most popular PUF architectures are transistor-based and they focus on exploiting the uncontrollable process variations in conventional CMOS fabrication technology. Recent development in emerging technology such as memristor-based models provides an opportunity to achieve a robust and lightweight PUF architecture. Memristor-based PUF has proven to be more resilient to attacks such as hardware reverse engineering attacks. In this paper, we design a lightweight and low-cost memristor PUF and verify it against cryptographic randomness tests achieving a unique, reliable, irreversible random sequence output. The current research demonstrates the architecture of a low-cost, high endurance Cu/HfO$$_2/p^{++}$$ 2 / p + + Si memristor-based PUF (MR-PUF) which is compatible with advanced CMOS technologies. This paper explores the 15 NIST cryptographic randomness tests that have been applied to our Cu/HfO$$_2/p^{++}$$ 2 / p + + Si MR-PUF. Moreover, security properties such as uniformity, uniqueness, and repeatability of our MR-PUF have been tested in this paper and validated. Additionally, this paper explores the applicability of our MR-PUF on block ciphers to improve the randomness achieved within the encryption process. Our MR-PUF has been used on block ciphers to construct a TRNG cipher block that successfully passed the NIST tests. Additionally, this paper investigated MR-PUF within a new authenticated key exchange and mutual authentication protocol between the head-end system (HES) and smart meters (SM)s in an advanced metering infrastructure (AMI) for smartgrids. The authenticated key exchange protocol utilized within the AMI was verified in this paper to meet the essential security when it comes to randomness by successfully passing the NIST tests without a post-processing algorithm.

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