1,417 research outputs found
Introducing Accountability to Anonymity Networks
Many anonymous communication (AC) networks rely on routing traffic through
proxy nodes to obfuscate the originator of the traffic. Without an
accountability mechanism, exit proxy nodes risk sanctions by law enforcement if
users commit illegal actions through the AC network. We present BackRef, a
generic mechanism for AC networks that provides practical repudiation for the
proxy nodes by tracing back the selected outbound traffic to the predecessor
node (but not in the forward direction) through a cryptographically verifiable
chain. It also provides an option for full (or partial) traceability back to
the entry node or even to the corresponding user when all intermediate nodes
are cooperating. Moreover, to maintain a good balance between anonymity and
accountability, the protocol incorporates whitelist directories at exit proxy
nodes. BackRef offers improved deployability over the related work, and
introduces a novel concept of pseudonymous signatures that may be of
independent interest.
We exemplify the utility of BackRef by integrating it into the onion routing
(OR) protocol, and examine its deployability by considering several
system-level aspects. We also present the security definitions for the BackRef
system (namely, anonymity, backward traceability, no forward traceability, and
no false accusation) and conduct a formal security analysis of the OR protocol
with BackRef using ProVerif, an automated cryptographic protocol verifier,
establishing the aforementioned security properties against a strong
adversarial model
Blocks\u27 Network: Redesign Architecture based on Blockchain Technology
The Internet is a global network that uses communication protocols. It is considered the most important system reached by humanity, which no one can abandon. However, this technology has become a weapon that threatens the privacy of users, especially in the client-server model, where data is stored and managed privately. Additionally, users have no power over their data that store in a private server, which means users’ data may interrupt by government or might be sold via service provider for-profit purposes. Furthermore, blockchain is a technology that we can rely on to solve issues related to client-server model if appropriately used. However, blockchain technology uses consensus protocol, which is used for creating an incontrovertible system of agreement between members across a distributed network. Thus, the consensus protocol is used to slow all member down from generating too fast in order to control the network creation pattern, which leads to scalability and latency problems.
The proposed system will present a platform that leverages modernize blockchain called Blocks’ Network. The system is taking into consideration the issues related to privacy and confidentiality from the client-side model, and scalability and latency issues from the blockchain technology side. Blocks’ network is a public and a permissioned network that use a multi-dimensional hash to generate multiple chains for the purpose of a systematic approach.
The proposed platform is an assembly point for users to create a decentralized network using P2P protocols. The system has high data flow due to frequent use by participants (for example, the use of the Internet). Besides, the system will store all traffic of the network overtly via Blocks’ Network
Some Implementation Issues for Security Services based on IBE
Identity Based Encryption (IBE) is a public key cryptosystem where a unique identity string, such as an e-mail address, can be used as a public key. IBE is simpler than the traditional PKI since certificates are not needed. An IBE scheme is usually based on pairing of discrete points on elliptic curves. An IBE scheme can also be based on quadratic residuosity. This paper presents an overview of these IBE schemes and surveys present IBE based security services. Private key management is described in detail with protocols to authenticate users of Private Key Generation Authorities (PKG), to protect submission of generated private keys, and to avoid the key escrow problem. In the security service survey IBE implementations for smartcards, for smart phones, for security services in mobile networking, for security services in health care information systems, for secure web services, and for grid network security are presented. Also the performance of IBE schemes is estimated
Anonymous and Adaptively Secure Revocable IBE with Constant Size Public Parameters
In Identity-Based Encryption (IBE) systems, key revocation is non-trivial.
This is because a user's identity is itself a public key. Moreover, the private
key corresponding to the identity needs to be obtained from a trusted key
authority through an authenticated and secrecy protected channel. So far, there
exist only a very small number of revocable IBE (RIBE) schemes that support
non-interactive key revocation, in the sense that the user is not required to
interact with the key authority or some kind of trusted hardware to renew her
private key without changing her public key (or identity). These schemes are
either proven to be only selectively secure or have public parameters which
grow linearly in a given security parameter. In this paper, we present two
constructions of non-interactive RIBE that satisfy all the following three
attractive properties: (i) proven to be adaptively secure under the Symmetric
External Diffie-Hellman (SXDH) and the Decisional Linear (DLIN) assumptions;
(ii) have constant-size public parameters; and (iii) preserve the anonymity of
ciphertexts---a property that has not yet been achieved in all the current
schemes
Accountable Metadata-Hiding Escrow: A Group Signature Case Study
Abstract
A common approach to demands for lawful access to encrypted data is to allow a trusted third party (TTP) to gain access to private data. However, there is no way to verify that this trust is well placed as the TTP may open all messages indiscriminately. Moreover, existing approaches do not scale well when, in addition to the content of the conversation, one wishes to hide one’s identity. Given the importance of metadata this is a major problem. We propose a new approach in which users can retroactively verify cryptographically whether they were wiretapped. As a case study, we propose a new signature scheme that can act as an accountable replacement for group signatures, accountable forward and backward tracing signatures.</jats:p
ClaimChain: Improving the Security and Privacy of In-band Key Distribution for Messaging
The social demand for email end-to-end encryption is barely supported by
mainstream service providers. Autocrypt is a new community-driven open
specification for e-mail encryption that attempts to respond to this demand. In
Autocrypt the encryption keys are attached directly to messages, and thus the
encryption can be implemented by email clients without any collaboration of the
providers. The decentralized nature of this in-band key distribution, however,
makes it prone to man-in-the-middle attacks and can leak the social graph of
users. To address this problem we introduce ClaimChain, a cryptographic
construction for privacy-preserving authentication of public keys. Users store
claims about their identities and keys, as well as their beliefs about others,
in ClaimChains. These chains form authenticated decentralized repositories that
enable users to prove the authenticity of both their keys and the keys of their
contacts. ClaimChains are encrypted, and therefore protect the stored
information, such as keys and contact identities, from prying eyes. At the same
time, ClaimChain implements mechanisms to provide strong non-equivocation
properties, discouraging malicious actors from distributing conflicting or
inauthentic claims. We implemented ClaimChain and we show that it offers
reasonable performance, low overhead, and authenticity guarantees.Comment: Appears in 2018 Workshop on Privacy in the Electronic Society
(WPES'18
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