Broadcast encryption is the cryptographic problem of delivering encrypted content (e.g. TV programs or data on DVDs) over a broadcast channel in such a way that only qualified users (e.g. subscribers who have paid their fees or DVD players conforming to a specification) can decrypt the content. [1] [2] [3] The challenge arises from the requirement that the set of qualified users can change in each broadcast emission, and therefore revocation of individual users or user groups should be possible using broadcast transmissions, only, and without affecting any remaining users. As efficient revocation is the primary objective of broadcast encryption, solutions are also referred to as revocation schemes. [4] [5] [6]
Rather than directly encrypting the content for qualified users, broadcast encryption schemes distribute keying information that allows qualified users to reconstruct the content encryption key whereas revoked users find insufficient information to recover the key. [1] The typical setting considered is that of a unidirectional broadcaster and stateless users (i.e., users do not keep bookmarking of previous messages by the broadcaster), which is especially challenging. [4] In contrast, the scenario where users are supported with a bi-directional communication link with the broadcaster and thus can more easily maintain their state, and where users are not only dynamically revoked but also added (joined), is often referred to as multicast encryption. [7]
The problem of practical broadcast encryption has first been formally studied by Amos Fiat and Moni Naor in 1994. [1] Since then, several solutions have been described in the literature, including combinatorial constructions, one-time revocation schemes based on secret sharing techniques, and tree-based constructions. [2] In general, they offer various trade-offs between the increase in the size of the broadcast, the number of keys that each user needs to store, and the feasibility of an unqualified user or a collusion of unqualified users being able to decrypt the content. Luby and Staddon have used a combinatorial approach to study the trade-offs for some general classes of broadcast encryption algorithms. [3] A particularly efficient tree-based construction is the "subset difference" scheme, which is derived from a class of so-called subset cover schemes. [4] The subset difference scheme is notably implemented in the AACS for HD DVD and Blu-ray Disc encryption. A rather simple broadcast encryption scheme is used for the CSS for DVD encryption.
The problem of rogue users sharing their decryption keys or the decrypted content with unqualified users is mathematically insoluble. Traitor tracing algorithms aim to minimize the damage by retroactively identifying the user or users who leaked their keys, so that punitive measures, legal or otherwise, may be undertaken. [8] [4] In practice, pay TV systems often employ set-top boxes with tamper-resistant smart cards that impose physical restraints on a user learning their own decryption keys. Some broadcast encryption schemes, such as AACS, also provide tracing capabilities. [9]
In cryptography, the International Data Encryption Algorithm (IDEA), originally called Improved Proposed Encryption Standard (IPES), is a symmetric-key block cipher designed by James Massey of ETH Zurich and Xuejia Lai and was first described in 1991. The algorithm was intended as a replacement for the Data Encryption Standard (DES). IDEA is a minor revision of an earlier cipher, the Proposed Encryption Standard (PES).
The International Association for Cryptologic Research (IACR) is a non-profit scientific organization that furthers research in cryptology and related fields. The IACR was organized at the initiative of David Chaum at the CRYPTO '82 conference.
A chosen-ciphertext attack (CCA) is an attack model for cryptanalysis where the cryptanalyst can gather information by obtaining the decryptions of chosen ciphertexts. From these pieces of information the adversary can attempt to recover the secret key used for decryption.
David Lee Chaum is an American computer scientist, cryptographer, and inventor. He is known as a pioneer in cryptography and privacy-preserving technologies, and widely recognized as the inventor of digital cash. His 1982 dissertation "Computer Systems Established, Maintained, and Trusted by Mutually Suspicious Groups" is the first known proposal for a blockchain protocol. Complete with the code to implement the protocol, Chaum's dissertation proposed all but one element of the blockchain later detailed in the Bitcoin whitepaper. He has been referred to as "the father of online anonymity", and "the godfather of cryptocurrency".
Identity-based encryption (IBE), is an important primitive of identity-based cryptography. As such it is a type of public-key encryption in which the public key of a user is some unique information about the identity of the user. This means that a sender who has access to the public parameters of the system can encrypt a message using e.g. the text-value of the receiver's name or email address as a key. The receiver obtains its decryption key from a central authority, which needs to be trusted as it generates secret keys for every user.
In cryptography, DES-X is a variant on the DES symmetric-key block cipher intended to increase the complexity of a brute-force attack. The technique used to increase the complexity is called key whitening.
Provable security refers to any type or level of computer security that can be proved. It is used in different ways by different fields.
Serge Vaudenay is a French cryptographer and professor, director of the Communications Systems Section at the École Polytechnique Fédérale de Lausanne
A deterministic encryption scheme is a cryptosystem which always produces the same ciphertext for a given plaintext and key, even over separate executions of the encryption algorithm. Examples of deterministic encryption algorithms include RSA cryptosystem, and many block ciphers when used in ECB mode or with a constant initialization vector.
A group signature scheme is a method for allowing a member of a group to anonymously sign a message on behalf of the group. The concept was first introduced by David Chaum and Eugene van Heyst in 1991. For example, a group signature scheme could be used by an employee of a large company where it is sufficient for a verifier to know a message was signed by an employee, but not which particular employee signed it. Another application is for keycard access to restricted areas where it is inappropriate to track individual employee's movements, but necessary to secure areas to only employees in the group.
Plaintext-awareness is a notion of security for public-key encryption. A cryptosystem is plaintext-aware if it is difficult for any efficient algorithm to come up with a valid ciphertext without being aware of the corresponding plaintext.
Digital credentials are the digital equivalent of paper-based credentials. Just as a paper-based credential could be a passport, a driver's license, a membership certificate or some kind of ticket to obtain some service, such as a cinema ticket or a public transport ticket, a digital credential is a proof of qualification, competence, or clearance that is attached to a person. Also, digital credentials prove something about their owner. Both types of credentials may contain personal information such as the person's name, birthplace, birthdate, and/or biometric information such as a picture or a finger print.
Distributed key generation (DKG) is a cryptographic process in which multiple parties contribute to the calculation of a shared public and private key set. Unlike most public key encryption models, distributed key generation does not rely on Trusted Third Parties. Instead, the participation of a threshold of honest parties determines whether a key pair can be computed successfully. Distributed key generation prevents single parties from having access to a private key. The involvement of many parties requires Distributed key generation to ensure secrecy in the presence of malicious contributions to the key calculation.
Moni Naor is an Israeli computer scientist, currently a professor at the Weizmann Institute of Science. Naor received his Ph.D. in 1989 at the University of California, Berkeley. His advisor was Manuel Blum.
Post-quantum cryptography (PQC), sometimes referred to as quantum-proof, quantum-safe, or quantum-resistant, is the development of cryptographic algorithms that are thought to be secure against a cryptanalytic attack by a quantum computer. Most widely-used public-key algorithms rely on the difficulty of one of three mathematical problems: the integer factorization problem, the discrete logarithm problem or the elliptic-curve discrete logarithm problem. All of these problems could be easily solved on a sufficiently powerful quantum computer running Shor's algorithm or even faster and less demanding alternatives.
Amos Fiat is an Israeli computer scientist, a professor of computer science at Tel Aviv University. He is known for his work in cryptography, online algorithms, and algorithmic game theory.
Mordechai M. "Moti" Yung is a cryptographer and computer scientist known for his work on cryptovirology and kleptography.
Matthew Keith "Matt" Franklin is an American cryptographer, and a professor of computer science at the University of California, Davis.
Amit Sahai is an Indian-American computer scientist. He is a professor of computer science at UCLA and the director of the Center for Encrypted Functionalities.
Orr Dunkelman is an Israeli cryptographer and cryptanalyst, currently a professor at the University of Haifa Computer Science department. Dunkelman is a co-director of the Center for Cyber Law & Privacy at the University of Haifa and a co-founder of Privacy Israel, an Israeli NGO for promoting privacy in Israel.
{{cite book}}
: |journal=
ignored (help){{cite book}}
: |journal=
ignored (help){{cite book}}
: |journal=
ignored (help)