56 research outputs found

    Security Analysis of RSA-BSSA

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    In a blind signature scheme, a user can obtain a digital signature on a message of her choice without revealing anything about the message or the resulting signature to the signer. Blind signature schemes have recently found applications for privacy-preserving web browsing and ad ecosystems, and as such, are ripe for standardization. In this paper, we show that the recent proposed standard of Denis, Jacobs and Wood [18, 17] constitutes a strongly one-more-unforgeable blind signature scheme in the random-oracle model under the one-more-RSA assumption. Fur- ther, we show that the blind version of RSA-FDH proposed and analyzed by Bellare, Namprempre, Pointcheval and Semanko [6] does not satisfy blindness when the public key is chosen maliciously, but satisfies a weaker notion of a blind token

    Everlasting ROBOT: the Marvin Attack

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    In this paper we show that Bleichenbacher-style attacks on RSA decryption are not only still possible, but also that vulnerable implementations are common. We have successfully attacked multiple implementations using only timing of decryption operation and shown that many others are vulnerable. To perform the attack we used more statistically rigorous techniques like the sign test, Wilcoxon signed-rank test, and bootstrapping of median of pairwise differences. We publish a set of tools for testing libraries that perform RSA decryption against timing side-channel attacks, including one that can test arbitrary TLS servers with no need to write a test harnesses. Finally, we propose a set of workarounds that implementations can employ if they can\u27t avoid the use of RSA

    Side-Channel Analysis and Cryptography Engineering : Getting OpenSSL Closer to Constant-Time

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    As side-channel attacks reached general purpose PCs and started to be more practical for attackers to exploit, OpenSSL adopted in 2005 a flagging mechanism to protect against SCA. The opt-in mechanism allows to flag secret values, such as keys, with the BN_FLG_CONSTTIME flag. Whenever a flag is checked and detected, the library changes its execution flow to SCA-secure functions that are slower but safer, protecting these secret values from being leaked. This mechanism favors performance over security, it is error-prone, and is obscure for most library developers, increasing the potential for side-channel vulnerabilities. This dissertation presents an extensive side-channel analysis of OpenSSL and criticizes its fragile flagging mechanism. This analysis reveals several flaws affecting the library resulting in multiple side-channel attacks, improved cache-timing attack techniques, and a new side channel vector. The first part of this dissertation introduces the main topic and the necessary related work, including the microarchitecture, the cache hierarchy, and attack techniques; then it presents a brief troubled history of side-channel attacks and defenses in OpenSSL, setting the stage for the related publications. This dissertation includes seven original publications contributing to the area of side-channel analysis, microarchitecture timing attacks, and applied cryptography. From an SCA perspective, the results identify several vulnerabilities and flaws enabling protocol-level attacks on RSA, DSA, and ECDSA, in addition to full SCA of the SM2 cryptosystem. With respect to microarchitecture timing attacks, the dissertation presents a new side-channel vector due to port contention in the CPU execution units. And finally, on the applied cryptography front, OpenSSL now enjoys a revamped code base securing several cryptosystems against SCA, favoring a secure-by-default protection against side-channel attacks, instead of the insecure opt-in flagging mechanism provided by the fragile BN_FLG_CONSTTIME flag

    Location Privacy in VANETs: Improved Chaff-Based CMIX and Privacy-Preserving End-to-End Communication

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    VANETs communication systems are technologies and defined policies that can be formed to enable ITS applications to provide road traffic efficacy, warning about such issues as environmental dangers, journey circumstances, and in the provision of infotainment that considerably enhance transportation safety and quality. The entities in VANETs, generally vehicles, form part of a massive network known as the Internet of Vehicles (IoV). The deployment of large-scale VANETs systems is impossible without ensuring that such systems are themselves are safe and secure, protecting the privacy of their users. There is a risk that cars might be hacked, or their sensors become defective, causing inaccurate information to be sent across the network. Consequently, the activities and credentials of participating vehicles should be held responsible and quickly broadcast throughout a vast VANETs, considering the accountability in the system. The openness of wireless communication means that an observer can eavesdrop on vehicular communication and gain access or otherwise deduce users' sensitive information, and perhaps profile vehicles based on numerous factors such as tracing their travels and the identification of their home/work locations. In order to protect the system from malicious or compromised entities, as well as to preserve user privacy, the goal is to achieve communication security, i.e., keep users' identities hidden from both the outside world and the security infrastructure and service providers. Being held accountable while still maintaining one's privacy is a difficult balancing act. This thesis explores novel solution paths to the above challenges by investigating the impact of low-density messaging to improve the security of vehicle communications and accomplish unlinkability in VANETs. This is achieved by proposing an improved chaff-based CMIX protocol that uses fake messages to increase density to mitigate tracking in this scenario. Recently, Christian \etall \cite{vaas2018nowhere} proposed a Chaff-based CMIX scheme that sends fake messages under the presumption low-density conditions to enhance vehicle privacy and confuse attackers. To accomplish full unlinkability, we first show the following security and privacy vulnerabilities in the Christian \etall scheme: linkability attacks outside the CMIX may occur due to deterministic data-sharing during the authentication phase (e.g., duplicate certificates for each communication). Adversaries may inject fake certificates, which breaks Cuckoo Filters' (CFs) updates authenticity, and the injection may be deniable. CMIX symmetric key leakage outside the coverage may occur. We propose a VPKI-based protocol to mitigate these issues. First, we use a modified version of Wang \etall's \cite{wang2019practical} scheme to provide mutual authentication without revealing the real identity. To this end, a vehicle's messages are signed with a different pseudo-identity “certificate”. Furthermore, the density is increased via the sending of fake messages during low traffic periods to provide unlinkability outside the mix-zone. Second, unlike Christian \etall's scheme, we use the Adaptive Cuckoo Filter (ACF) instead of CF to overcome the effects of false positives on the whole filter. Moreover, to prevent any alteration of the ACFs, only RUSs distribute the updates, and they sign the new fingerprints. Third, mutual authentication prevents any leakage from the mix zones' symmetric keys by generating a fresh one for each communication through a Diffie–Hellman key exchange. As a second main contribution of this thesis, we focus on the V2V communication without the interference of a Trusted Third Party (TTP)s in case this has been corrupted, destroyed, or is out of range. This thesis presents a new and efficient end-to-end anonymous key exchange protocol based on Yang \etall's \cite{yang2015self} self-blindable signatures. In our protocol, vehicles first privately blind their own private certificates for each communication outside the mix-zone and then compute an anonymous shared key based on zero-knowledge proof of knowledge (PoK). The efficiency comes from the fact that once the signatures are verified, the ephemeral values in the PoK are also used to compute a shared key through an authenticated Diffie-Hellman key exchange protocol. Therefore, the protocol does not require any further external information to generate a shared key. Our protocol also does not require interfacing with the Roadside Units or Certificate Authorities, and hence can be securely run outside the mixed-zones. We demonstrate the security of our protocol in ideal/real simulation paradigms. Hence, our protocol achieves secure authentication, forward unlinkability, and accountability. Furthermore, the performance analysis shows that our protocol is more efficient in terms of computational and communications overheads compared to existing schemes.Kuwait Cultural Offic

    One Truth Prevails: A Deep-learning Based Single-Trace Power Analysis on RSA–CRT with Windowed Exponentiation

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    In this paper, a deep-learning based power/EM analysis attack on the state-of-the-art RSA–CRT software implementation is proposed. Our method is applied to a side-channel-aware implementation with the Gnu Multi-Precision (MP) Library, which is a typical open-source software library. Gnu MP employs a fixed-window exponentiation, which is the fastest in a constant time, and loads the entire precomputation table once to avoid side-channel leaks from multiplicands. To conduct an accurate estimation of secret exponents, our method focuses on the process of loading the entire precomputation table, which we call a dummy load scheme. It is particularly noteworthy that the dummy load scheme is implemented as a countermeasure against a simple power/EM analysis (SPA/SEMA). This type of vulnerability from a dummy load scheme also exists in other cryptographic libraries. We also propose a partial key exposure attack suitable for the distribution of errors inthe secret exponents recovered from the windowed exponentiation. We experimentally show that the proposed method consisting of the above power/EM analysis attack, as well as a partial key exposure attack, can be used to fully recover the secret key of the RSA–CRT from the side-channel information of a single decryption or a signature process

    Eesti elektrooniline ID-kaart ja selle turvaväljakutsed

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    Eesti elektrooniline isikutunnistust (ID-kaart) on üle 18 aasta pakkunud turvalist elektroonilist identiteeti Eesti kodanikele. Avaliku võtme krüptograafia ja kaardile talletatud privaatvõti võimaldavad ID-kaardi omanikel juurde pääseda e-teenustele, anda juriidilist jõudu omavaid digiallkirju ning elektrooniliselt hääletada. Käesolevas töös uuritakse põhjalikult Eesti ID-kaarti ning sellega seotud turvaväljakutseid. Me kirjeldame Eesti ID-kaarti ja selle ökosüsteemi, seotud osapooli ja protsesse, ID-kaardi elektroonilist baasfunktsionaalsust, seotud tehnilisi ja juriidilisi kontseptsioone ning muid seotud küsimusi. Me tutvustame kõiki kasutatud kiipkaardiplatforme ja nende abil väljastatud isikutunnistuste tüüpe. Iga platformi kohta esitame me detailse analüüsi kasutatava asümmeetrilise krüptograafia funktsionaalsusest ning kirjeldame ja analüüsime ID-kaardi kauguuendamise lahendusi. Lisaks esitame me süstemaatilise uurimuse ID-kaardiga seotud turvaintsidentidest ning muudest sarnastest probleemidest läbi aastate. Me kirjeldame probleemide tehnilist olemust, kasutatud leevendusmeetmeid ning kajastust ajakirjanduses. Käesoleva uurimustöö käigus avastati mitmeid varem teadmata olevaid turvaprobleeme ning teavitati nendest seotud osapooli. Käesolev töö põhineb avalikult kättesaadaval dokumentatsioonil, kogutud ID-kaartide sertifikaatide andmebaasil, ajakirjandusel,otsesuhtlusel seotud osapooltega ning töö autori analüüsil ja eksperimentidel.For more than 18 years, the Estonian electronic identity card (ID card) has provided a secure electronic identity for Estonian residents. The public-key cryptography and private keys stored on the card enable Estonian ID card holders to access e-services, give legally binding digital signatures and even cast an i-vote in national elections. This work provides a comprehensive study on the Estonian ID card and its security challenges. We introduce the Estonian ID card and its ecosystem by describing the involved parties and processes, the core electronic functionality of the ID card, related technical and legal concepts, and the related issues. We describe the ID card smart card chip platforms used over the years and the identity document types that have been issued using these platforms. We present a detailed analysis of the asymmetric cryptography functionality provided by each ID card platform and present a description and security analysis of the ID card remote update solutions that have been provided for each ID card platform. As yet another contribution of this work, we present a systematic study of security incidents and similar issues the Estonian ID card has experienced over the years. We describe the technical nature of the issue, mitigation measures applied and the reflections on the media. In the course of this research, several previously unknown security issues were discovered and reported to the involved parties. The research has been based on publicly available documentation, collection of ID card certificates in circulation, information reflected in media, information from the involved parties, and our own analysis and experiments performed in the field.https://www.ester.ee/record=b541416

    JackHammer: Efficient Rowhammer on Heterogeneous FPGA-CPU Platforms

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    After years of development, FPGAs are finally making an appearance on multi-tenant cloud servers. These heterogeneous FPGA-CPU architectures break common assumptions about isolation and security boundaries. Since the FPGA and CPU architectures share hardware resources, a new class of vulnerabilities requires us to reassess the security and dependability of these platforms. In this work, we analyze the memory and cache subsystem and study Rowhammer and cache attacks enabled on two proposed heterogeneous FPGA-CPU platforms by Intel: the Arria 10 GX with an integrated FPGA-CPU platform, and the Arria 10 GX PAC expansion card which connects the FPGA to the CPU via the PCIe interface. We show that while Intel PACs currently are immune to cache attacks from FPGA to CPU, the integrated platform is indeed vulnerable to Prime and Probe style attacks from the FPGA to the CPU's last level cache. Further, we demonstrate JackHammer, a novel and efficient Rowhammer from the FPGA to the host's main memory. Our results indicate that a malicious FPGA can perform twice as fast as a typical Rowhammer attack from the CPU on the same system and causes around four times as many bit flips as the CPU attack. We demonstrate the efficacy of JackHammer from the FPGA through a realistic fault attack on the WolfSSL RSA signing implementation that reliably causes a fault after an average of fifty-eight RSA signatures, 25% faster than a CPU rowhammer attack. In some scenarios our JackHammer attack produces faulty signatures more than three times more often and almost three times faster than a conventional CPU rowhammer attack.Comment: Accepted to IACR Transactions on Cryptographic Hardware and Embedded Systems (TCHES), Volume 2020, Issue

    A DPA Attack against Asymmetric Encryption: RSA Attacks and Countermeasures

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    Abstract This paper discusses side-channel attacks based on Power Analysis. This approach utilizes physical side effects of using cryptographic functions in the real world. A side channel is a source of information that is inherent to a physical implementation of cryptographic functions. Research done in the last half of the 1990s has shown that the information transmitted by side channels, such as execution time, computational faults and power consumption, can be disadvantageous to the security of cryptosystem like RSA or AES. This paper surveys the techniques of Differential Power Analysis presented i
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