Table Of ContentStudies in Computational Intelligence 965
Muhammad Habib ur Rehman
Mohamed Medhat Gaber Editors
Federated
Learning
Systems
Towards Next-Generation AI
Studies in Computational Intelligence
Volume 965
Series Editor
Janusz Kacprzyk, Polish Academy of Sciences, Warsaw, Poland
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Muhammad Habib ur Rehman
(cid:129)
Mohamed Medhat Gaber
Editors
Federated Learning Systems
Towards Next-Generation AI
123
Editors
Muhammad Habib urRehman MohamedMedhat Gaber
Centerfor Cyber-Physical Systems Schoolof Computing
KhalifaUniversity of Science andDigital Technology
andTechnology Birmingham City University
AbuDhabi, UnitedArab Emirates Birmingham, UK
ISSN 1860-949X ISSN 1860-9503 (electronic)
Studies in Computational Intelligence
ISBN978-3-030-70603-6 ISBN978-3-030-70604-3 (eBook)
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Preface
BusinessesandGovernmentsarecollectingmassivedataabouttheircustomersand
citizens. These organizations store the data in centralized cloud storage infras-
tructures to perform large-scale training to make complex and timely decisions.
This data collection process remains continuous; however, customers and citizens
always show their concerns about the data management and processing.
Considering this, several regulatory measures were taken and various laws were
approvedbyGovernmentssuchastheEuropeanUnion(GDPR),theUnited States
ofAmerica(HIPAA/CCPA),andCanada(PIPDEA).However,still,thecustomers
and citizens are raising concerns over their privacy protection and false decisions
made by machine learning systems. Therefore, the inability to collect fresh data
poses a serious threat to well-informed and realistic decisions.
Google introduced the term federated learning (FL) to enable the machine
learning models to be initially trained at the customers’ or citizens’ devices and
systemsandlaterthemodelupdatesareaggregatedatthecentralizedcloudservers.
Considering this notion of FL, a large plethora of research activities has been
performed by researchers and practitioners in academia and industry. Hence,
numerousresearchpublicationswereproducedtosolvetheactiveresearchissuesin
termsofprivacy,security,dataandmodelsynchronization,modeldevelopmentand
deployment, personalization, incentivization, and heterogeneity across the FL
systems.
This book aims to study the FL ecosystem with a broader perspective to cover
the theoretical as well as applied aspects of FL systems. Therefore, this book is
structured into eight chapters in total. In the first chapter, Ali et al. performed a
thoroughbibliometricanalysisofthefieldofFL.Authorshaveconductedthorough
researchoftheScopusdatabasetouncoverthepublicationtrends.Theyfound476
scholarlydocumentsintotalandthenanalyzedthedatasettofindthegrowthtrends
in FL research. Also, they studied subject areas and ranked them in terms of the
numberofpublications.Also,theyoutlinedthetop-10citedpapers,top-10authors,
top-10institutions,andtop-10countries.Moreover,theycategorizedthedocuments
into various types and then uncovered the top-10 sources of these documents.
Finally, the authors have performed the domain profiling of the FL research area
vii
viii Preface
and they identified five hot domains such as the internet of things (IoT), wireless
communication,privacyandsecurity,dataanalytics,andlearningandoptimization,
where most of the FL research has been creating impact. Christopher et al., in
Chap.2,reviewFLasanapproachforperformingmachinelearningondistributed
data to protect the privacy of user-generated data. They highlight pertinent chal-
lengesinanIoTcontextsuchasreducingcommunicationcostsassociatedwithdata
transmission, learning from data under heterogeneous conditions, and applying
additional privacy protections to FL. Throughout this review, they identify the
strengths and weaknesses of different methods applied to FL, and finally, they
outline future directions for privacy-preserving FL research, particularly focusing
on IoT applications.
Toeffectivelypreventinformationleakage,K.Weietal.(inChap.3)investigate
a differential privacy mechanism in which, at the clients’ side, artificial noises are
added to parameters before uploading. Moreover, they propose a K-client random
schedulingpolicy,inwhichKclientsarerandomlyselectedfromatotalofNclients
toparticipateineachcommunicationround.Furthermore,atheoreticalconvergence
bound is derived from the loss function of the trained FL model. In detail, con-
sidering a fixed privacy level, the theoretical bound reveals that there exist an
optimalnumberofclientsKthatcanachievethebestconvergenceperformancedue
to the tradeoff between the volume of user data and the variances of aggregated
artificial noises. To optimize this tradeoff, they further provide a differentially
private FL-based client selection (DP-FedCS) algorithm, which can dynamically
select the number of training clients. Their experimental results validate their the-
oretical conclusions and also show that the proposed algorithm can effectively
improve both the FL training efficiency and FL model quality for a given privacy
protection level.
FL provides privacy-by-design. It trains a machine learning model collabora-
tivelyoverseveraldistributedclients(rangingfromtwotomillions)suchasmobile
phones, without sharing their raw data with any other participant. In practical
scenarios, all clients do not have sufficient computing resources (e.g., Internet of
Things), the machine learning model has millions of parameters, and its privacy
between the server and the clients while training/testing is a prime concern (e.g.,
rivalparties).Inthisregard,FLisnotsufficient,sosplitlearning(SL)isintroduced
in Chap. 4 by C. Thapa et al. SL is reliable in these scenarios as it splits a model
into multiple portions, distributes them among clients and server, and trains/tests
theirrespectivemodelportionstoaccomplishthefullmodeltraining/testing.InSL,
the participants do not share both data and their model portions with any other
parties,andusually,asmallernetworkportionisassignedtotheclientswheredata
resides.Recently,ahybridofFLandSL,calledSplitFedlearning,isintroducedto
elevatethebenefitsofbothFL(fastertraining/testingtime)andSL(modelsplitand
training). Following the developments from FL to SL, and considering the
importanceofSL,thischapterisdesignedtoprovideextensivecoverageinSLand
itsvariants.Thecoverageincludesfundamentals,existingfindings,integrationwith
privacy measures such as differential privacy, open problems, and code
implementation.
Preface ix
Chapter 5 presents the practitioner view on FL research whereby a group of
researchersfromthePySyftCommunityhaselaboratedonthekeyfeaturesoftheir
FL tool. PySyft is an open-source multi-language library enabling secure and pri-
vate machine learning by wrapping and extending popular deep learning frame-
works such as PyTorch in a transparent, lightweight, and user-friendly manner. Its
aimistobothhelppopularizeprivacy-preservingtechniquesinmachinelearningby
making them as accessible as possible via Python bindings and common tools
familiartoresearchersanddatascientists,aswellastobeextensiblesuchthatnew
FederatedLearning,Multi-Party Computation,orDifferential Privacymethods can
beflexiblyandsimplyimplementedandintegrated.Thischapterwillintroducethe
methods available within the PySyft library and describe their implementations.
The authors also provide a proof-of-concept demonstration of an FL workflow
usinganexampleofhowtotrainaconvolutionalneuralnetwork.Next,reviewthe
use of PySyft in academic literature to date and discuss future use-cases and
development plans. Most importantly, they introduce Duet: their tool for easier
federated learning for scientists and data owners.
Inthemedicalorhealthcareindustry,wherethealreadyavailableinformationor
data is never sufficient, decisions can be performed with the help of FL by
empowering AI models to learn on private data without conceding privacy. The
primaryobjectiveofChap.6istohighlighttheadaptabilityandworkingoftheFL
techniques in the healthcare system especially in drug development, clinical diag-
nosis, digital health monitoring, and various disease predictions and detection
system.Thefirstsectionofthechaptercomprisedofmotivation,FLforhealthcare,
FLworkingmodelinhealthcare,andvariousbenefitsofFL.Thenextsectionofthe
chapter described the reported work which highlights the working of different
researchers who used the FL model. The final section of the chapter presented the
comparativeanalysisofdifferentFLalgorithmsfordifferenthealthsectorsbyusing
parameters such as accuracy, the area under the curve, precision, recall, and
F-score. Ahmed et al., in Chap. 7, envision the idea of fully decentralized FL
system. They emphasized on using blockchain-empowered smart contract tech-
nologies to enable fairness and trust among the FL participants over underlying
peer-to-peer networks.
Finally, David and Zaid in Chap. 8 analyze existing vulnerabilities of FL and
subsequently perform a literature review of the possible attack methods targeting
FL privacy protection capabilities. These attack methods are then categorized by a
basic taxonomy. Additionally, they provide a literature study of the most recent
defensivestrategiesandalgorithms for FLaimedtoovercomethese attacks.These
defensive strategies are categorized by their respective underlying defense princi-
ple. The chapteradvocatesthat theapplicationofasingledefensivestrategy isnot
enough to provide adequate protection against all available attack methods.
Althoughthisbookprimarilytargetsthecomputerscience,informationtechnology,
and data science communities. However, considering the generalized content, this
bookwillbeequallyhelpfulforthestudents,researchers,andpractitionersfromall
walksoflife.SincethisisthefirstcontributedresearchbookonthetopicofFL,we
aim to include more important and active research topics in the future editions of
x Preface
this book. Finally, we would like to thank and acknowledge the efforts of all
contributors including authors, reviewers, and editorial staff for putting their
untiring efforts into making this project a success.
Abu Dhabi, United Arab Emirates Muhammad Habib ur Rehman
Birmingham, UK Mohamed Medhat Gaber
December 2020
