Biblio
In the dawn of crypto-currencies the most talked currency is Bitcoin. Bitcoin is widely flourished digital currency and an exchange trading commodity implementing peer-to-peer payment network. No central athourity exists in Bitcoin. The users in network or pool of bitcoin need not to use real names, rather they use pseudo names for managing and verifying transactions. Due to the use of pseudo names bitcoin is apprehended to provide anonymity. However, the most transparent payment network is what bitcoin is. Here all the transactions are publicly open. To furnish wholeness and put a stop to double-spending, Blockchain is used, which actually works as a ledger for management of Bitcoins. Blockchain can be misused to monitor flow of bitcoins among multiple transactions. When data from external sources is amalgamated with insinuation acquired from the Blockchain, it may result to reveal user's identity and profile. In this way the activity of user may be traced to an extent to fraud that user. Along with the popularity of Bitcoins the number of adversarial attacks has also gain pace. All these activities are meant to exploit anonymity and privacy in Bitcoin. These acivities result in loss of bitcoins and unlawful profit to attackers. Here in this paper we tried to present analysis of major attacks such as malicious attack, greater than 52% attacks and block withholding attack. Also this paper aims to present analysis and improvements in Bitcoin's anonymity and privacy.
Accountable authority identity-based encryption (A-IBE), as an attractive way to guarantee the user privacy security, enables a malicious private key generator (PKG) to be traced if it generates and re-distributes a user private key. Particularly, an A-IBE scheme achieves full black-box security if it can further trace a decoder box and is secure against a malicious PKG who can access the user decryption results. In PKC'11, Sahai and Seyalioglu presented a generic construction for full black-box A-IBE from a primitive called dummy identity-based encryption, which is a hybrid between IBE and attribute-based encryption (ABE). However, as the complexity of ABE, their construction is inefficient and the size of private keys and ciphertexts in their instantiation is linear in the length of user identity. In this paper, we present a new efficient generic construction for full black-box A-IBE from a new primitive called token-based identity-based encryption (TB-IBE), without using ABE. We first formalize the definition and security model for TB-IBE. Subsequently, we show that a TB-IBE scheme satisfying some properties can be converted to a full black-box A-IBE scheme, which is as efficient as the underlying TB-IBE scheme in terms of computational complexity and parameter sizes. Finally, we give an instantiation with the computational complexity as O(1) and the constant size master key pair, private keys, and ciphertexts.
Cloud computing is a standard architecture for providing computing services among servers and cloud user (CU) for preserving data from unauthorized users. Therefore, the user authentication is more reliable to ensure cloud services accessed only by a genuine user. To improve the authentication accuracy, Tiger Hash-based Kerberos Biometric Blowfish Authentication (TH-KBBA) Mechanism is introduced for accessing data from server. It comprises three steps, namely Registration, Authentication and Ticket Granting. In the Registration process, client enrolls user details and stores on cloud server (CS) using tiger hashing function. User ID and password is given by CS after registration. When client wants to access data from CS, authentication server (AS) verifies user identity by sending a message. When authenticity is verified, AS accepts user as authenticated user and convinces CS that user is authentic. For convincing process, AS generates a ticket and encrypted using Blowfish encryption. Encrypted ticket is sent back to user. Then, CU sends message to server containing users ID and encrypted ticket. Finally, the server decrypts ticket using blowfish decryption and verifies the user ID. If these two ID gets matched, the CS grants requested data to the user. Experimental evaluation of TH-KBBA mechanism and existing methods are carried out with different factors such as Authentication accuracy, authentications time and confidentiality rate with respect to a number of CUs and data.
In the future Internet of Things, it is envisioned that things are collaborating to serve people. Unfortunately, this vision could not be realised without relations between things and people. To solve the problem this paper proposes a user centric identity management system that incorporates user identity, device identity and the relations between them. The proposed IDM system is user centric and allows device authentication and authorization based on the user identity. A typical compelling use case of the proposed solution is also given.