Unit:
Διαπανεπιστημιακό ΠΜΣ Λογική και Θεωρία Αλγορίθμων και ΥπολογισμούLibrary of the School of Science
Author:
Σάμαρη Αικατερίνη
Supervisors info:
Άγγελος Κιαγιάς Επίκ. Καθηγ.
Original Title:
Encryption mechanisms for multiuser environments
Summary:
As the title indicates, this thesis is related to the role of encryption in
multiuser environments. Specifically, we
concentrate on issues related to a class of encryption schemes called Broadcast
Encryption. Assume that a sender wishes to send messages to a large group of
recipients via a broadcast channel in a way that he
can choose a subset from a set of designated receivers on the fly and enable
them to decrypt a ciphertext while simultaneously preventing any
other party from doing so. The schemes that achieve this goal can be divided
into two categories, combinatorial schemes and schemes based on algebraic
structures, structured schemes. We refer to several examples of each category
with different performance trade-offs. Furthermore, we provide the necessary
security definitions for these schemes.
The state-of-the-art broadcast encryption schemes do not aim to address the
feature of privacy, i.e. in each transmission they do not hide the enabled set
which means that the revoked users can learn the members of the enabled set
even though they cannot decrypt the message. The main part of this thesis
focuses on the feature of privacy in the setting of broadcast encryption. We
present work that has been done related to this property
and then we present
some new results which came up during the preparation of this thesis.
We provide a definitional framework for privacy notions and then we proceed by
giving some lower bounds on the
ciphertext length for private broadcast encryption schemes with respect to the
stated privacy definitions. Our main result is an impossibility result that
highlights the cost of privacy in the ciphertext size for atomic broadcast
encryption schemes (which include the class of combinatorial schemes).
Keywords:
Broadcast encryption, Privacy, Lower bounds
File:
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document.pdf
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File access is restricted only to the intranet of UoA.
