In fog computing, various connected devices of Internet-of-Things paradigm, share content with designated nearby fog devices for short term analytics. In this scenario, Ciphertext Policy-Attribute Based Encryption (CP-ABE) provides a secure content sharing mechanism by associating cryptographic secret keys with attributes assigned to each fog device by the system admin. For fail-safe transmission, if a fog device is about to become unavailable, it may need to delegate its keys to another device. Traditional CP-ABE supports key delegation but can't handle key leakage, leaving the whole system insecure and unstable. In this work, an efficient key delegation CP-ABE scheme with key leakage resistance has been proposed for fog computing. The scheme fully prevents key and protect unauthorised access. The results show that the proposed scheme is computationally efficient and secure. The encryption and decryption times are not increased by the proposed additional key leakage protection mechanism. Thus, the scheme enhances flexibility in content sharing in fog computing environment.

Electronic Health Records (EHRs) are the digitized form of a patient's health related information and reports in the repository of a healthcare provider. Among the numerous advantages of EHRs, the main disrupting one is real time sharing of health history in case of an emergency when a person has to be admitted to another healthcare provider. Sharing is a complex process, as the security, access control and integrity of the health data needs to be ensured. In this paper, a scheme has been designed to transfer temporary access to the emergency healthcare organization and revoke it after the treatment is over. Authenticated access grant and revocation is designed using Ciphertext Policy - Attribute Based Encryption (CP-ABE) and data encryption has been done using state-of-art symmetric encryption. Evaluation of the scheme shows that it does not incur much computational time overhead with an increasing number of attributes in the access policy. The scheme supports one to many encryption and dynamic policy updation to provide access of EHRs to external entities in real time. Forward secrecy is maintained without any redistribution of keys after revocation.

Secret keys are the cornerstone of any encrypted communication. In multicast cryptosystems like Attribute based Encryption (ABE), secret keys are assigned to users as per their attributes. Delegation of rights is a useful feature in collaborative environments and thus needs to be developed for ABE based systems also. In this work, we define the distinguishing key delegation features in existing Ciphertext Policy based ABE schemes. Specifically, the controlled delegation and key abuse aspects have been analyzed. Popular existing schemes have been evaluated with respect to these aspects as well as security models considered. In the process, some gaps were identified in existing key delegation approaches and are presented in this work.

The proliferation of the internet of medical things (IoMT) is proving to be a disruptive technology in contemporary healthcare. However, given the sensitivity of the nature of data being shared in this system security, and privacy are critical issues. Attribute-based encryption is a proactive technique for efficient one-to-many data sharing. Specifically, multi-authority-ciphertext policy-attribute-based encryption (MA-CP-ABE) is a suitable method given the multi-stakeholder ecosystem of IoMT-based healthcare. In this work, conventional MA-CP-ABE techniques have been modified to address several existing security limitations. To the best of our knowledge, the proposed work is first to address fault tolerance in MA-CP-ABE, without any redundancy at attribute authority's level and to develop a mechanism for full and partial revocation of compromised authority. A non-monotonic fully hidden access structure further enhances the security of the scheme while efficiently performing encryption/decryption operations even for a large number of attributes, making it suitable for the secure sharing of IoMT data.

Internet of Things(IoT) based systems and applications are nowadays being enabled by paradigm of edge or fog computing. Central authority controlling the system formulates the policy about which fog device will get data from which IoT device/s. As fog devices have attributes like physical location, storage capacity, computing capability etc, attribute based access policy can be enforced on each IoT data. Ciphertext Policy – Attribute Based Encryption (CP-ABE) is a method to implement the access policies. However, number of access trees becomes equal to the number of access policies. In this paper, hierarchy present in attribute sets of access policies has been exploited to obtain single integrated access policy. A content sharing protocol named Hierarchical Efficient Encryption at Edge (HE3) is worked out to implement the concept. The proposed protocol is demonstrated to be highly efficient in terms of encryption and decryption time as compared to existing approaches. A formal security proof is provided to establish strength of encryption.

Ciphertext Policy-Attribute Based Encryption (CP-ABE) is a secure one-to-many asymmetric encryption schemes where access control of a shared resource is defined in terms of a set of attributes possessed by a user. Key delegation service, where a user is able to temporally transfer its full or partial access rights, is an important requirement to make CP-ABE based systems practically useful. In existing CP-ABE delegation schemes, a delegator can delegate its entire or partial set of attributes such that all content accessible using those attributes becomes available to the delegatee also. Flexibility to delegate some specific content, which is a practical requirement, is not feasible with these schemes. Further, for a delegated resource, flexibility of fine grained delegation like delegating only a specific subset of read, write and update permissions is not yet available. In this work, CP-ABE key delegation has been enhanced to support specific content and specific permission delegation. The proposed scheme is fully flexible as it additionally supports limits on the number of times delegation can be done, delegatee revocation and traceability of forbidden delegation. Theoretical and practical analysis show that the proposed scheme achieves its objectives and is computationally efficient as well as secure against chosen plaintext and key abuse attacks.

Secret sharing is an integral part of CP-ABE implementation. Currently, Linear Secret Sharing Scheme (LSSS) and Lagrange interpolation are used in existing CP-ABE implementation. Implementation is complex and computational cost is high for generating the access tree structure using these schemes. In this paper, a novel construction of CP-ABE has been developed which implements counting based secret share generation and reconstruction method to generate access tree structure and reconstruct secret shares. The proposed development reduces the cost of access structure generation and reconstruction of secret and improves security by generating the large number of secret shares for small-sized secret. Hence, the new construction enhances the efficiency of encryption and decryption operations of CP-ABE.

In the cloud computing environment, Multi authority Ciphertext Policy-Attribute Based Encryption (CP-ABE) schemes are used as a key escrow free solution to securely and efficiently share data over cloud. However, the length of ciphertext in existing Multi Authority-CP-ABE schemes increases with the number of attributes in the access policy. Moreover, these schemes do not protect against dishonest attribute authorities. In this paper, a constant length ciphertext Multi Authority-CP-ABE scheme is proposed that reduces the communication overhead over the network. The scheme also prevents dishonest authority from compromising the system. Apart from this, for enhanced privacy of receivers, the access policy is communicated in hidden form. Thus, the presented scheme provides an efficient corrupt resistant, key escrow free Multi Authority-CP-ABE scheme by generating constant length ciphertext and hidden access structure. Results demonstrate the enhanced security and reduced cost of encryption and decryption by 8% and 48% respectively as compared to other existing works.

Secret sharing techniques are basis of construction of cryptographic operations like secure multi party computation and attribute based encryption. It involves distributing secret data as shares such that during reconstruction all of the shares are required. Threshold secret sharing requires a subset of shares to be used for reconstruction of master secret. Langrage interpolation and Chinese remainder theorem based secret shares generation are popular techniques used in literature. However, these techniques suffer from high computational complexity of share generation and secret reconstruction. In this work, we propose a computationally simple threshold secret sharing technique using matrices. The technique enhances security of existing comparable mechanism by generating a larger number of shares for small sized secrets while incurring little overhead of increase in size of each share.

Ciphertext Policy Attribute Based Encryption techniques provide fine grained access control to securely share the data in the organizations where access rights of users vary according to their roles. We have noticed that various key delegation mechanisms are provided for CP-ABE schemes but no key delegation mechanism exists for CP-ABE with hidden access policy. In practical, users' identity may be revealed from access policy in the organizations and unlimited further delegations may results in unauthorized data access. For maintaining the users' anonymity, the access structure should be hidden and every user must be restricted for specified further delegations. In this work, we have presented a flexible secure key delegation mechanism for CP-ABE with hidden access structure. The proposed scheme enhances the capability of existing CP-ABE schemes by supporting flexible delegation, attribute revocation and user revocation with negligible enhancement in computational cost.

Fog networking enables applications to execute directly on the edge devices (routers, set-top-boxes etc.) located near Internet of Things (IoT) devices, which reduces the load of cloud server and service latency time. The data captured from various IoTs may be accessible to all nearby fog devices Ciphertext Policy-Attribute Based Encryption (CP-ABE) offers a flexible solution to securely and publicly share data contents. In existing CP-ABE schemes, an entity can delegate its access rights to another which may lead to undesirable situation that infringes access policy. In this work, we propose a secure key delegation mechanism for fog networking which implements checks on delegation as well as instantaneous revocation. It also provides for flexibility for allowing or disallowing further delegation by delegated user. A case study requiring access of shared contents by fog devices has been implemented that supports flexible attribute delegation and revocation. The results demonstrate that our scheme improves the functionality of legacy CP-ABE and performance by providing threaded solution that supports concurrent execution.

Ciphertext Policy-Attribute Based Encryption (CP-ABE) is a public key encryption system that provides a flexible solution for sharing data files securely and publicly. As compared to conventional encryption CP-ABE generates single encrypted file that can be decrypted by anyone posing right attribute levels. In this paper, we have transformed legacy CP-ABE library to Object Oriented (OO) approach for enhancing the functionality of Ciphertext Policy-Attribute Based Encryption. CP-ABE has been further implemented as Multithreaded - Ciphertext Policy - Attribute Based Encryption (OOM-CP-ABE) for concurrency. Scope of parallelization in encryption and decryption operations has been exploited to obtain more efficient encryption and decryption. A case study for multilevel accessing of shared data files in a software company has been implemented to demonstrate the usefulness of implemented library. Experimental simulations demonstrate improved performance of proposed OOM-CP-ABE scheme to provide real time data encryption and decryption services as compared to legacy CP-ABE and OO-CP-ABE approaches.

Ciphertext Policy-Attribute Based Encryption (CP-ABE) is an emerging encryption technology to address challenges of secure data sharing. In this paper, a CP-ABE based scheme has been implemented for fine grained access control of documents in a typical university setup. The documents are encrypted with an embedded access structure and can be decrypted by only those users whose attribute values satisfy the access structure defined for the document. Experimental simulations demonstrate the capability of proposed solution in providing real time encryption/ decryption services on varying number of attributes, file sizes and types.

Resampling is used to calculate pixel values when one raster grid is fitted to another. High-resolution remote sensing satellite images contain more information in the discrete samples and after resampling process, it is desirable that the reconstructed image should maintain the same sharpness as the original image. Although several techniques are available, but it is essential to determine the best one for maintaining the sharpness and the pixel break at higher magnification level for photographic and digital display of high resolution satellite images. To preserve image quality, the interpolating function used for the resampling should be an ideal low-pass filter. In order to determine the best interpolation function, different resampling functions, namely Nearest Neighbor (NN), Bilinear (BL), Cubic Convolution ( α = 0 ), High-resolution Cubic Spline with Edge Enhancement ( α = -1 ), High-resolution Cubic Spline ( α = -0.5 ), Cubic Spline ( α = -2 ), Cubic Spline ( α = -.3/4), Cubic B-spline, Catmull-Rom Cubic, Quadratic Interpolation and Approximating Quadratic B-Spline have been analyzed on different spatial resolution Indian Remote Sensing (IRS) satellite images (LISS-III, LISS-IV and CARTOSAT-1). Performance of the above resampling methods has been evaluated by Visual interpretation, Digital Number Percentage (DN %) Analysis as well as other parameters likes Entropy and Image Noise Index (INI), MSE and PSNR. Investigation results have shown that with the change in the image processing operation, spatial resolution and evaluation parameter, the performance of resampling method changes, thereby emphasizing the need to judiciously select the resampling method.

This research paper examines memory managementissues associated with Smart card EEPROM and proposes a newtechnique for memory management for smart card files. Theentire work concentrates to suggest a new methodology onmemory allocation and de-allocation using pointers, which givesbetter memory utilization.