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Laurent Amsaleg - IEEE Xplore Author Profile

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Mixup is a powerful data augmentation method that in-terpolates between two or more examples in the input or feature space and between the corresponding target labels. However, how to best interpolate images is not well defined. Recent mixup methods overlay or cut-and-paste two or more objects into one image, which needs care in selecting regions. Mixup has also been connected to autoencoders, bec...Show More
Machine learning systems are vulnerable to adversarial attack. By applying to the input object a small, carefully-designed perturbation, a classifier can be tricked into making an incorrect prediction. This phenomenon has drawn wide interest, with many attempts made to explain it. However, a complete understanding is yet to emerge. In this paper we adopt a slightly different perspective, still rel...Show More
Adversarial examples of deep neural networks are receiving ever increasing attention because they help in understanding and reducing the sensitivity to their input. This is natural given the increasing applications of deep neural networks in our everyday lives. When white-box attacks are almost always successful, it is typically only the distortion of the perturbations that matters in their evalua...Show More
This paper proposes a framework for group membership protocols preventing the curious but honest server from reconstructing the enrolled biometric signatures and inferring the identity of querying clients. This framework learns the embedding parameters, group representations and assignments simultaneously. Experiments show the trade-off between security/privacy and verification/identification perf...Show More
When convoking privacy, group membership verification checks if a biometric trait corresponds to one member of a group without revealing the identity of that member. Similarly, group membership identification states which group the individual belongs to, without knowing his/her identity. A recent contribution provides privacy and security for group membership protocols through the joint use of two...Show More
Group membership verification checks if a biometric trait corresponds to one member of a group without revealing the identity of that member. Recent contributions provide privacy for group membership protocols through the joint use of two mechanisms: quantizing templates into discrete embeddings, and aggregating several templates into one group representation.However, this scheme has one drawback:...Show More
This paper proposes a group membership verification protocol preventing the curious but honest server from reconstructing the enrolled signatures and inferring the identity of querying clients. The protocol quantizes the signatures into discrete embeddings, making reconstruction difficult. It also aggregates multiple embeddings into representative values, impeding identification. Theoretical and e...Show More
Recent research has shown that machine learning systems, including state-of-the-art deep neural networks, are vulnerable to adversarial attacks. By adding to the input object an imperceptible amount of adversarial noise, it is highly likely that the classifier can be tricked into assigning the modified object to any desired class. It has also been observed that these adversarial samples generalize...Show More
This work proposes a privacy-protection framework for an important application called outsourced media search. This scenario involves a data owner, a client, and an untrusted server, where the owner outsources a search service to the server. Due to lack of trust, the privacy of the client and the owner should be protected. The framework relies on multimedia hashing and symmetric encryption. It req...Show More
The huge amount of redundant multimedia data, like video, has become a problem in terms of both space and copyright. Usually, the methods for identifying near-duplicate videos are neither adequate nor scalable to find pairs of similar videos. Similarity self-join operation could be an alternative to solve this problem in which all similar pairs of elements from a video dataset are retrieved. Nonet...Show More
We propose a privacy protection framework for large-scale content-based information retrieval. It offers two layers of protection. First, robust hash values are used as queries to prevent revealing original content or features. Second, the client can choose to omit certain bits in a hash value to further increase the ambiguity for the server. Due to the reduced information, it is computationally d...Show More
Content-based image retrieval systems typically rely on a similarity measure between image vector representations, such as in bag-of-words, to rank the database images in decreasing order of expected relevance to the query. However, the inherent asymmetry of k-nearest neighborhoods is not properly accounted for by traditional similarity measures, possibly leading to a loss of retrieval accuracy. T...Show More
Similarity search in high dimensional space database is split into two worlds: i) fast, scalable, and approximate search algorithms which are not secure, and ii) search protocols based on secure computation which are not scalable. This paper presents a one-way privacy protocol that lies in between these two worlds. Approximate metrics for the cosine similarity allows speed. Elements of large rando...Show More
While the past decade has witnessed an unprecedented growth of data generated and collected all over the world, existing data management approaches lack the ability to address the challenges of Big Data. One of the most promising tools for Big Data processing is the MapReduce paradigm. Although it has its limitations, the MapReduce programming model has laid the foundations for answering some of t...Show More
While high-dimensional search-by-similarity techniques reached their maturity and in overall provide good performance, most of them are unable to cope with very large multimedia collections. The `big data' challenge however has to be addressed as multimedia collections have been explosively growing and will grow even faster than ever within the next few years. Luckily, computational processing pow...Show More
Content-Based Image Retrieval Systems (CBIRS) used in forensics related contexts require very good image recognition capabilities. Whereas the robustness criterion has been extensively covered by Computer Vision or Multimedia literature, none of these communities explored the security of CBIRS. Recently, preliminary studies have shown real systems can be deluded by applying transformations to imag...Show More
This paper describes an initial study where the open-source Hadoop parallel and distributed run-time environment is used to speedup the construction phase of a large high-dimensional index. This paper first discusses the typical practical problems developers may run into when porting their code to Hadoop. It then presents early experimental results showing that the performance gains are substantia...Show More
As digital image collections have been growing ever larger, the multimedia community has put emphasis on methods for image content analysis and presentation. To facilitate extensive user studies of these methods, a single platform is needed that can uniformly incorporate all the analysis and presentation methods under study. Due to its extensibility features, a plug-in API for image analysis metho...Show More
Many algorithms for approximate nearest neighbor search in high-dimensional spaces partition the data into clusters. At query time, for efficiency, an index selects the few (or a single) clusters nearest to the query point. Clusters are often produced by the well-known k-means approach since it has several desirable properties. On the downside, it tends to produce clusters having quite different c...Show More
Recent indexing techniques inspired by source coding have been shown successful to index billions of high-dimensional vectors in memory. In this paper, we propose an approach that re-ranks the neighbor hypotheses obtained by these compressed-domain indexing methods. In contrast to the usual post-verification scheme, which performs exact distance calculation on the short-list of hypotheses, the est...Show More
Content-Based Image Retrieval (CBIR) has been recently used as a filtering mechanism against the piracy of multimedia contents. Many publications in the last few years have proposed very robust schemes where pirated contents are detected despite severe modifications. As none of these systems have addressed the piracy problem from a security perspective, it is time to check whether they are secure:...Show More
Over the last two decades, much research effort has been spent on nearest neighbor search in high-dimensional data sets. Most of the approaches published thus far have, however, only been tested on rather small collections. When large collections have been considered, high-performance environments have been used, in particular systems with a large main memory. Accessing data on disk has largely be...Show More
Recently, some approximate high-dimensional indexing techniques have shown promising results by trading off quality guarantees for improved query performance. While the query performance of these methods has been well studied, however, the performance of index maintenance has not yet been reported in any detail. In this paper we focus on the dynamic behavior of the NV-tree, which is a disk-based a...Show More
It is well known that high-dimensional nearest-neighbor retrieval is very expensive. Many signal processing methods suffer from this computing cost. Dramatic performance gains can be obtained by using approximate search, such as the popular Locality-Sensitive Hashing. This paper improves LSH by performing an on-line selection of the most appropriate hash functions from a pool of functions. An addi...Show More
Research in content-based multimedia retrieval needs to be a joint venture between the multimedia processing and database communities, in order to be usable in practice at a realistic scale. Unfortunately, however, while both communities have performed some excellent research, they have done so in isolation from each other. In this paper we describe the lessons learned from the Eff2 project on Eff...Show More