Visible to the public Biblio

Found 351 results

Filters: First Letter Of Title is F  [Clear All Filters]
A B C D E [F] G H I J K L M N O P Q R S T U V W X Y Z   [Show ALL]
F
Tsoutsos, N.G., Maniatakos, M..  2014.  Fabrication Attacks: Zero-Overhead Malicious Modifications Enabling Modern Microprocessor Privilege Escalation. Emerging Topics in Computing, IEEE Transactions on. 2:81-93.

The wide deployment of general purpose and embedded microprocessors has emphasized the need for defenses against cyber-attacks. Due to the globalized supply chain, however, there are several stages where a processor can be maliciously modified. The most promising stage, and the hardest during which to inject the hardware trojan, is the fabrication stage. As modern microprocessor chips are characterized by very dense, billion-transistor designs, such attacks must be very carefully crafted. In this paper, we demonstrate zero overhead malicious modifications on both high-performance and embedded microprocessors. These hardware trojans enable privilege escalation through execution of an instruction stream that excites the necessary conditions to make the modification appear. The minimal footprint, however, comes at the cost of a small window of attack opportunities. Experimental results show that malicious users can gain escalated privileges within a few million clock cycles. In addition, no system crashes were reported during normal operation, rendering the modifications transparent to the end user.
 

Chi, H., Hu, Y. H..  2015.  Face de-identification using facial identity preserving features. 2015 IEEE Global Conference on Signal and Information Processing (GlobalSIP). :586–590.

Automated human facial image de-identification is a much needed technology for privacy-preserving social media and intelligent surveillance applications. Other than the usual face blurring techniques, in this work, we propose to achieve facial anonymity by slightly modifying existing facial images into "averaged faces" so that the corresponding identities are difficult to uncover. This approach preserves the aesthesis of the facial images while achieving the goal of privacy protection. In particular, we explore a deep learning-based facial identity-preserving (FIP) features. Unlike conventional face descriptors, the FIP features can significantly reduce intra-identity variances, while maintaining inter-identity distinctions. By suppressing and tinkering FIP features, we achieve the goal of k-anonymity facial image de-identification while preserving desired utilities. Using a face database, we successfully demonstrate that the resulting "averaged faces" will still preserve the aesthesis of the original images while defying facial image identity recognition.

Patoliya, J. J., Desai, M. M..  2017.  Face detection based ATM security system using embedded Linux platform. 2017 2nd International Conference for Convergence in Technology (I2CT). :74–78.

In order to provide reliable security solution to the people, the concept of smart ATM security system based on Embedded Linux platform is suggested in this paper. The study is focused on Design and Implementation of Face Detection based ATM Security System using Embedded Linux Platform. The system is implemented on the credit card size Raspberry Pi board with extended capability of open source Computer Vision (OpenCV) software which is used for Image processing operation. High level security mechanism is provided by the consecutive actions such as initially system captures the human face and check whether the human face is detected properly or not. If the face is not detected properly, it warns the user to adjust him/her properly to detect the face. Still the face is not detected properly the system will lock the door of the ATM cabin for security purpose. As soon as the door is lock, the system will automatic generates 3 digit OTP code. The OTP code will be sent to the watchman's registered mobile number through SMS using GSM module which is connected with the raspberry Pi. Watchman will enter the generated OTP through keypad which is interfaced with the Pi Board. The OTP will be verified and if it is correct then door will be unlock otherwise it will remain lock.

Feng, Ranran, Prabhakaran, Balakrishnan.  2016.  On the "Face of Things". Proceedings of the 2016 ACM on International Conference on Multimedia Retrieval. :3–4.

Face is crucial for human identity, while face identification has become crucial to information security. It is important to understand and work with the problems and challenges for all different aspects of facial feature extraction and face identification. In this tutorial, we identify and discuss four research challenges in current Face Detection/Recognition research and related research areas: (1) Unavoidable Facial Feature Alterations, (2) Voluntary Facial Feature Alterations, (3) Uncontrolled Environments, and (4) Accuracy Control on Large-scale Dataset. We also direct several different applications (spin-offs) of facial feature studies in the tutorial.

Nakashima, Y., Koyama, T., Yokoya, N., Babaguchi, N..  2015.  Facial expression preserving privacy protection using image melding. 2015 IEEE International Conference on Multimedia and Expo (ICME). :1–6.

An enormous number of images are currently shared through social networking services such as Facebook. These images usually contain appearance of people and may violate the people's privacy if they are published without permission from each person. To remedy this privacy concern, visual privacy protection, such as blurring, is applied to facial regions of people without permission. However, in addition to image quality degradation, this may spoil the context of the image: If some people are filtered while the others are not, missing facial expression makes comprehension of the image difficult. This paper proposes an image melding-based method that modifies facial regions in a visually unintrusive way with preserving facial expression. Our experimental results demonstrated that the proposed method can retain facial expression while protecting privacy.

Yang, Xinli, Li, Ming, Zhao, ShiLin.  2017.  Facial Expression Recognition Algorithm Based on CNN and LBP Feature Fusion. Proceedings of the 2017 International Conference on Robotics and Artificial Intelligence. :33–38.
When a complex scene such as rotation within a plane is encountered, the recognition rate of facial expressions will decrease much. A facial expression recognition algorithm based on CNN and LBP feature fusion is proposed in this paper. Firstly, according to the problem of the lack of feature expression ability of CNN in the process of expression recognition, a CNN model was designed. The model is composed of structural units that have two successive convolutional layers followed by a pool layer, which can improve the expressive ability of CNN. Then, the designed CNN model was used to extract the facial expression features, and local binary pattern (LBP) features with rotation invariance were fused. To a certain extent, it makes up for the lack of CNN sensitivity to in-plane rotation changes. The experimental results show that the proposed method improves the expression recognition rate under the condition of plane rotation to a certain extent and has better robustness.
Liu, Peng, Zhao, Siqi, Li, Songbin.  2017.  Facial Expression Recognition Based On Hierarchical Feature Learning. Proceedings of the 2017 2Nd International Conference on Communication and Information Systems. :309–313.
Facial expression recognition is a challenging problem in the field of computer vision. In this paper, we propose a deep learning approach that can learn the joint low-level and high-level features of human face to resolve this problem. Our deep neural networks utilize convolution and downsampling to extract the abstract and local features of human face, and reconstruct the raw input images to learn global features as supplementary information at the same time. We also add an adjustable weight in the networks when combining the two kinds of features for the final classification. The experimental results show that the proposed method can achieve good results, which has an average recognition accuracy of 93.65% on the test datasets.
Pan, Bowen, Wang, Shangfei.  2018.  Facial Expression Recognition Enhanced by Thermal Images Through Adversarial Learning. Proceedings of the 26th ACM International Conference on Multimedia. :1346–1353.
Currently, fusing visible and thermal images for facial expression recognition requires two modalities during both training and testing. Visible cameras are commonly used in real-life applications, and thermal cameras are typically only available in lab situations due to their high price. Thermal imaging for facial expression recognition is not frequently used in real-world situations. To address this, we propose a novel thermally enhanced facial expression recognition method which uses thermal images as privileged information to construct better visible feature representation and improved classifiers by incorporating adversarial learning and similarity constraints during training. Specifically, we train two deep neural networks from visible images and thermal images. We impose adversarial loss to enforce statistical similarity between the learned representations of two modalities, and a similarity constraint to regulate the mapping functions from visible and thermal representation to expressions. Thus, thermal images are leveraged to simultaneously improve visible feature representation and classification during training. To mimic real-world scenarios, only visible images are available during testing. We further extend the proposed expression recognition method for partially unpaired data to explore thermal images' supplementary role in visible facial expression recognition when visible images and thermal images are not synchronously recorded. Experimental results on the MAHNOB Laughter database demonstrate that our proposed method can effectively regularize visible representation and expression classifiers with the help of thermal images, achieving state-of-the-art recognition performance.
Wang, XuMing, Huang, Jin, Zhu, Jia, Yang, Min, Yang, Fen.  2018.  Facial Expression Recognition with Deep Learning. Proceedings of the 10th International Conference on Internet Multimedia Computing and Service. :10:1–10:4.
Automatic recognition of facial expression images is a challenge for computer due to variation of expression, background, position and label noise. The paper propose a new method for static facial expression recognition. Main process is to perform experiments by FER-2013 dataset, the primary mission is using our CNN model to classify a set of static images into 7 basic emotions and then achieve effective classification automatically. The two preprocessing of the faces picture have enhanced the effect of the picture for recognition. First, FER datasets are preprocessed with standard histogram eqialization. Then we employ ImageDataGenerator to deviate and rotate the facial image to enhance model robustness. Finally, the result of softmax activation function (also known as multinomial logistic regression) is stacked by SVM. The result of softmax activation function + SVM is better than softmax activation function. The accuracy of facial expression recognition achieve 68.79% on the test set.
Wu, Chongliang, Wang, Shangfei, Pan, Bowen, Chen, Huaping.  2016.  Facial Expression Recognition with Deep Two-view Support Vector Machine. Proceedings of the 2016 ACM on Multimedia Conference. :616–620.

This paper proposes a novel deep two-view approach to learn features from both visible and thermal images and leverage the commonality among visible and thermal images for facial expression recognition from visible images. The thermal images are used as privileged information, which is required only during training to help visible images learn better features and classifier. Specifically, we first learn a deep model for visible images and thermal images respectively, and use the learned feature representations to train SVM classifiers for expression classification. We then jointly refine the deep models as well as the SVM classifiers for both thermal images and visible images by imposing the constraint that the outputs of the SVM classifiers from two views are similar. Therefore, the resulting representations and classifiers capture the inherent connections among visible facial image, infrared facial image and target expression labels, and hence improve the recognition performance for facial expression recognition from visible images during testing. Experimental results on the benchmark expression database demonstrate the effectiveness of our proposed method.

Wu, Yue.  2016.  Facial Landmark Detection and Tracking for Facial Behavior Analysis. Proceedings of the 2016 ACM on International Conference on Multimedia Retrieval. :431–434.

The face is the most dominant and distinct communication tool of human beings. Automatic analysis of facial behavior allows machines to understand and interpret a human's states and needs for natural interactions. This research focuses on developing advanced computer vision techniques to process and analyze facial images for the recognition of various facial behaviors. Specifically, this research consists of two parts: automatic facial landmark detection and tracking, and facial behavior analysis and recognition using the tracked facial landmark points. In the first part, we develop several facial landmark detection and tracking algorithms on facial images with varying conditions, such as varying facial expressions, head poses and facial occlusions. First, to handle facial expression and head pose variations, we introduce a hierarchical probabilistic face shape model and a discriminative deep face shape model to capture the spatial relationships among facial landmark points under different facial expressions and face poses to improve facial landmark detection. Second, to handle facial occlusion, we improve upon the effective cascade regression framework and propose the robust cascade regression framework for facial landmark detection, which iteratively predicts the landmark visibility probabilities and landmark locations. The second part of this research applies our facial landmark detection and tracking algorithms to facial behavior analysis, including facial action recognition and face pose estimation. For facial action recognition, we introduce a novel regression framework for joint facial landmark detection and facial action recognition. For head pose estimation, we are working on a robust algorithm that can perform head pose estimation under facial occlusion.

Amato, Giuseppe, Carrara, Fabio, Falchi, Fabrizio, Gennaro, Claudio, Vairo, Claudio.  2018.  Facial-based Intrusion Detection System with Deep Learning in Embedded Devices. Proceedings of the 2018 International Conference on Sensors, Signal and Image Processing. :64–68.
With the advent of deep learning based methods, facial recognition algorithms have become more effective and efficient. However, these algorithms have usually the disadvantage of requiring the use of dedicated hardware devices, such as graphical processing units (GPUs), which pose restrictions on their usage on embedded devices with limited computational power. In this paper, we present an approach that allows building an intrusion detection system, based on face recognition, running on embedded devices. It relies on deep learning techniques and does not exploit the GPUs. Face recognition is performed using a knn classifier on features extracted from a 50-layers Residual Network (ResNet-50) trained on the VGGFace2 dataset. In our experiment, we determined the optimal confidence threshold that allows distinguishing legitimate users from intruders. In order to validate the proposed system, we created a ground truth composed of 15,393 images of faces and 44 identities, captured by two smart cameras placed in two different offices, in a test period of six months. We show that the obtained results are good both from the efficiency and effectiveness perspective.
Wang, Jun, Arriaga, Afonso, Tang, Qiang, Ryan, Peter Y.A..  2018.  Facilitating Privacy-Preserving Recommendation-as-a-Service with Machine Learning. Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security. :2306–2308.

Machine-Learning-as-a-Service has become increasingly popular, with Recommendation-as-a-Service as one of the representative examples. In such services, providing privacy protection for the users is an important topic. Reviewing privacy-preserving solutions which were proposed in the past decade, privacy and machine learning are often seen as two competing goals at stake. Though improving cryptographic primitives (e.g., secure multi-party computation (SMC) or homomorphic encryption (HE)) or devising sophisticated secure protocols has made a remarkable achievement, but in conjunction with state-of-the-art recommender systems often yields far-from-practical solutions. We tackle this problem from the direction of machine learning. We aim to design crypto-friendly recommendation algorithms, thus to obtain efficient solutions by directly using existing cryptographic tools. In particular, we propose an HE-friendly recommender system, refer to as CryptoRec, which (1) decouples user features from latent feature space, avoiding training the recommendation model on encrypted data; (2) only relies on addition and multiplication operations, making the model straightforwardly compatible with HE schemes. The properties turn recommendation-computations into a simple matrix-multiplication operation. To further improve efficiency, we introduce a sparse-quantization-reuse method which reduces the recommendation-computation time by \$9$\backslash$times\$ (compared to using CryptoRec directly), without compromising the accuracy. We demonstrate the efficiency and accuracy of CryptoRec on three real-world datasets. CryptoRec allows a server to estimate a user's preferences on thousands of items within a few seconds on a single PC, with the user's data homomorphically encrypted, while its prediction accuracy is still competitive with state-of-the-art recommender systems computing over clear data. Our solution enables Recommendation-as-a-Service on large datasets in a nearly real-time (seconds) level.

Sheppard, J. W., Strasser, S..  2017.  A factored evolutionary optimization approach to Bayesian abductive inference for multiple-fault diagnosis. 2017 IEEE AUTOTESTCON. :1–10.
When supporting commercial or defense systems, a perennial challenge is providing effective test and diagnosis strategies to minimize downtime, thereby maximizing system availability. Potentially one of the most effective ways to maximize downtime is to be able to detect and isolate as many faults in a system at one time as possible. This is referred to as the "multiple-fault diagnosis" problem. While several tools have been developed over the years to assist in performing multiple-fault diagnosis, considerable work remains to provide the best diagnosis possible. Recently, a new model for evolutionary computation has been developed called the "Factored Evolutionary Algorithm" (FEA). In this paper, we combine our prior work in deriving diagnostic Bayesian networks from static fault isolation manuals and fault trees with the FEA strategy to perform abductive inference as a way of addressing the multiple-fault diagnosis problem. We demonstrate the effectiveness of this approach on several networks derived from existing, real-world FIMs.
Huang, L., Chen, J., Zhu, Q..  2017.  A Factored MDP Approach to Optimal Mechanism Design for Resilient Large-Scale Interdependent Critical Infrastructures. 2017 Workshop on Modeling and Simulation of Cyber-Physical Energy Systems (MSCPES). :1–6.

Enhancing the security and resilience of interdependent infrastructures is crucial. In this paper, we establish a theoretical framework based on Markov decision processes (MDPs) to design optimal resiliency mechanisms for interdependent infrastructures. We use MDPs to capture the dynamics of the failure of constituent components of an infrastructure and their cyber-physical dependencies. Factored MDPs and approximate linear programming are adopted for an exponentially growing dimension of both state and action spaces. Under our approximation scheme, the optimally distributed policy is equivalent to the centralized one. Finally, case studies in a large-scale interdependent system demonstrate the effectiveness of the control strategy to enhance the network resilience to cascading failures.

Hammi, B., Khatoun, R., Doyen, G..  2014.  A Factorial Space for a System-Based Detection of Botcloud Activity. New Technologies, Mobility and Security (NTMS), 2014 6th International Conference on. :1-5.

Today, beyond a legitimate usage, the numerous advantages of cloud computing are exploited by attackers, and Botnets supporting DDoS attacks are among the greatest beneficiaries of this malicious use. Such a phenomena is a major issue since it strongly increases the power of distributed massive attacks while involving the responsibility of cloud service providers that do not own appropriate solutions. In this paper, we present an original approach that enables a source-based de- tection of UDP-flood DDoS attacks based on a distributed system behavior analysis. Based on a principal component analysis, our contribution consists in: (1) defining the involvement of system metrics in a botcoud's behavior, (2) showing the invariability of the factorial space that defines a botcloud activity and (3) among several legitimate activities, using this factorial space to enable a botcloud detection.

Hammi, B., Khatoun, R., Doyen, G..  2014.  A Factorial Space for a System-Based Detection of Botcloud Activity. New Technologies, Mobility and Security (NTMS), 2014 6th International Conference on. :1-5.

Today, beyond a legitimate usage, the numerous advantages of cloud computing are exploited by attackers, and Botnets supporting DDoS attacks are among the greatest beneficiaries of this malicious use. Such a phenomena is a major issue since it strongly increases the power of distributed massive attacks while involving the responsibility of cloud service providers that do not own appropriate solutions. In this paper, we present an original approach that enables a source-based de- tection of UDP-flood DDoS attacks based on a distributed system behavior analysis. Based on a principal component analysis, our contribution consists in: (1) defining the involvement of system metrics in a botcoud's behavior, (2) showing the invariability of the factorial space that defines a botcloud activity and (3) among several legitimate activities, using this factorial space to enable a botcloud detection.

Baum, Tobias, Liskin, Olga, Niklas, Kai, Schneider, Kurt.  2016.  Factors Influencing Code Review Processes in Industry. Proceedings of the 2016 24th ACM SIGSOFT International Symposium on Foundations of Software Engineering. :85–96.

Code review is known to be an efficient quality assurance technique. Many software companies today use it, usually with a process similar to the patch review process in open source software development. However, there is still a large fraction of companies performing almost no code reviews at all. And the companies that do code reviews have a lot of variation in the details of their processes. For researchers trying to improve the use of code reviews in industry, it is important to know the reasons for these process variations. We have performed a grounded theory study to clarify process variations and their rationales. The study is based on interviews with software development professionals from 19 companies. These interviews provided insights into the reasons and influencing factors behind the adoption or non-adoption of code reviews as a whole as well as for different process variations. We have condensed these findings into seven hypotheses and a classification of the influencing factors. Our results show the importance of cultural and social issues for review adoption. They trace many process variations to differences in development context and in desired review effects.

Yanbing Liu, Qingyun Liu, Ping Liu, Jianlong Tan, Li Guo.  2014.  A factor-searching-based multiple string matching algorithm for intrusion detection. Communications (ICC), 2014 IEEE International Conference on. :653-658.

Multiple string matching plays a fundamental role in network intrusion detection systems. Automata-based multiple string matching algorithms like AC, SBDM and SBOM are widely used in practice, but the huge memory usage of automata prevents them from being applied to a large-scale pattern set. Meanwhile, poor cache locality of huge automata degrades the matching speed of algorithms. Here we propose a space-efficient multiple string matching algorithm BVM, which makes use of bit-vector and succinct hash table to replace the automata used in factor-searching-based algorithms. Space complexity of the proposed algorithm is O(rm2 + ΣpϵP |p|), that is more space-efficient than the classic automata-based algorithms. Experiments on datasets including Snort, ClamAV, URL blacklist and synthetic rules show that the proposed algorithm significantly reduces memory usage and still runs at a fast matching speed. Above all, BVM costs less than 0.75% of the memory usage of AC, and is capable of matching millions of patterns efficiently.

Yanbing Liu, Qingyun Liu, Ping Liu, Jianlong Tan, Li Guo.  2014.  A factor-searching-based multiple string matching algorithm for intrusion detection. Communications (ICC), 2014 IEEE International Conference on. :653-658.

Multiple string matching plays a fundamental role in network intrusion detection systems. Automata-based multiple string matching algorithms like AC, SBDM and SBOM are widely used in practice, but the huge memory usage of automata prevents them from being applied to a large-scale pattern set. Meanwhile, poor cache locality of huge automata degrades the matching speed of algorithms. Here we propose a space-efficient multiple string matching algorithm BVM, which makes use of bit-vector and succinct hash table to replace the automata used in factor-searching-based algorithms. Space complexity of the proposed algorithm is O(rm2 + ΣpϵP |p|), that is more space-efficient than the classic automata-based algorithms. Experiments on datasets including Snort, ClamAV, URL blacklist and synthetic rules show that the proposed algorithm significantly reduces memory usage and still runs at a fast matching speed. Above all, BVM costs less than 0.75% of the memory usage of AC, and is capable of matching millions of patterns efficiently.

Zakaria, I., Mustaha, H..  2017.  FADETPM: Novel approach of file assured deletion based on trusted platform module. 2017 3rd International Conference of Cloud Computing Technologies and Applications (CloudTech). :1–4.
Nowadays, the Internet is developed, so that the requirements for on- and offline data storage have increased. Large storage IT projects, are related to large costs and high level of business risk. A storage service provider (SSP) provides computer storage space and management. In addition to that, it offers also back-up and archiving. Despite this, many companies fears security, privacy and integrity of outsourced data. As a solution, File Assured Deletion (FADE) is a system built upon standard cryptographic issues. It aims to guarantee their privacy and integrity, and most importantly, assuredly deleted files to make them unrecoverable to anybody (including those who manage the cloud storage) upon revocations of file access policies, by encrypting outsourced data files. Unfortunately, This system remains weak, in case the key manager's security is compromised. Our work provides a new scheme that aims to improve the security of FADE by using the TPM (Trusted Platform Module) that stores safely keys, passwords and digital certificates.
Chen, S., Wang, T., Ai, J..  2015.  A fair exchange and track system for RFID-tagged logistic chains. 2015 8th International Conference on Biomedical Engineering and Informatics (BMEI). :661–666.

RFID (Radio-Frequency IDentification) is attractive for the strong visibility it provides into logistics operations. In this paper, we explore fair-exchange techniques to encourage honest reporting of item receipt in RFID-tagged supply chains and present a fair ownership transfer system for RFID-tagged supply chains. In our system, a receiver can only access the data and/or functions of the RFID tag by providing the sender with a cryptographic attestation of successful receipt; cheating results in a defunct tag. Conversely, the sender can only obtain the receiver's attestation by providing the secret keys required to access the tag.

Yifrach, Assaf, Mansour, Yishay.  2018.  Fair Leader Election for Rational Agents in Asynchronous Rings and Networks. Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing. :217–226.

We study a game theoretic model where a coalition of processors might collude to bias the outcome of the protocol, where we assume that the processors always prefer any legitimate outcome over a non-legitimate one. We show that the problems of Fair Leader Election and Fair Coin Toss are equivalent, and focus on Fair Leader Election. Our main focus is on a directed asynchronous ring of n processors, where we investigate the protocol proposed by Abraham et al. [4] and studied in Afek et al. [5]. We show that in general the protocol is resilient only to sub-linear size coalitions. Specifically, we show that Ω( p n logn) randomly located processors or Ω( 3 √ n) adversarially located processors can force any outcome. We complement this by showing that the protocol is resilient to any adversarial coalition of size O( 4 √ n). We propose a modification to the protocol, and show that it is resilient to every coalition of size ?( √ n), by exhibiting both an attack and a resilience result. For every k ≥ 1, we define a family of graphs Gk that can be simulated by trees where each node in the tree simulates at most k processors. We show that for every graph in Gk , there is no fair leader election protocol that is resilient to coalitions of size k. Our result generalizes a previous result of Abraham et al. [4] that states that for every graph, there is no fair leader election protocol which is resilient to coalitions of size ?n/2 ?.

Dziembowski, Stefan, Eckey, Lisa, Faust, Sebastian.  2018.  FairSwap: How To Fairly Exchange Digital Goods. Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security. :967-984.

We introduce FairSwap – an efficient protocol for fair exchange of digital goods using smart contracts. A fair exchange protocol allows a sender S to sell a digital commodity x for a fixed price p to a receiver R. The protocol is said to be secure if R only pays if he receives the correct x. Our solution guarantees fairness by relying on smart contracts executed over decentralized cryptocurrencies, where the contract takes the role of an external judge that completes the exchange in case of disagreement. While in the past there have been several proposals for building fair exchange protocols over cryptocurrencies, our solution has two distinctive features that makes it particular attractive when users deal with large commodities. These advantages are: (1) minimizing the cost for running the smart contract on the blockchain, and (2) avoiding expensive cryptographic tools such as zero-knowledge proofs. In addition to our new protocols, we provide formal security definitions for smart contract based fair exchange, and prove security of our construction. Finally, we illustrate several applications of our basic protocol and evaluate practicality of our approach via a prototype implementation for fairly selling large files over the cryptocurrency Ethereum. This article is summarized in: the morning paper an interesting/influential/important paper from the world of CS every weekday morning, as selected by Adrian Colyer