Affine Determinant Programs: A Framework for Obfuscation and Witness Encryption

An affine determinant program ADP: {0,1}^n → {0,1} is specified by a tuple (A,B_1,...,B_n) of square matrices over F_q and a function Eval: F_q → {0,1}, and evaluated on x \in {0,1}^n by computing Eval(det(A + sum_{i \in [n]} x_i B_i)). In this work, we suggest ADPs as a new framework for building general-purpose obfuscation and witness encryption. We provide evidence to suggest that constructions following our ADP-based framework may one day yield secure, practically feasible obfuscation. As a proof-of-concept, we give a candidate ADP-based construction of indistinguishability obfuscation (iO) for all circuits along with a simple witness encryption candidate. We provide cryptanalysis demonstrating that our schemes resist several potential attacks, and leave further cryptanalysis to future work. Lastly, we explore practically feasible applications of our witness encryption candidate, such as public-key encryption with near-optimal key generation

Privacy Preserving Image Registration

Image registration is a key task in medical imaging applications, allowing to represent medical images in a common spatial reference frame. Current literature on image registration is generally based on the assumption that images are usually accessible to the researcher, from which the spatial transformation is subsequently estimated. This common assumption may not be met in current practical applications, since the sensitive nature of medical images may ultimately require their analysis under privacy constraints, preventing to share the image content in clear form. In this work, we formulate the problem of image registration under a privacy preserving regime, where images are assumed to be confidential and cannot be disclosed in clear. We derive our privacy preserving image registration framework by extending classical registration paradigms to account for advanced cryptographic tools, such as secure multi-party computation and homomorphic encryption, that enable the execution of operations without leaking the underlying data. To overcome the problem of performance and scalability of cryptographic tools in high dimensions, we first propose to optimize the underlying image registration operations using gradient approximations. We further revisit the use of homomorphic encryption and use a packing method to allow the encryption and multiplication of large matrices more efficiently. We demonstrate our privacy preserving framework in linear and non-linear registration problems, evaluating its accuracy and scalability with respect to standard image registration. Our results show that privacy preserving image registration is feasible and can be adopted in sensitive medical imaging applications

RAISE THE STRENGTH OF CRYPTOSYSTEM USING VARIETY EFFECTS

Nowadays, images became one of the most types of transmitted data through Internet. Some of these images carry secret information, therefore having an effective cryptosystem for hiding the information inside these images become an urgent need. Many traditional encryption methods are unable to achieve a high degree of protection for information. This paper presents nontraditional method for image encryption through applying substitution and transposition operations in different ways on both key and data. Series of (Linear and Circular), (Left, Right, Up and Down) rotation operations on (Bits and Bytes) of key and data are applied to make good confusion effects in the data. Moreover, XOR Boolean operations also applied on the key and data to make diffusion effects in the data. These two types of operations will produce a large set of keys. Using this large number of different keys in encrypting image will raise the strength of the encryption system used and achieve a high degree of protection for image. To test the security degree and performance of the encryption system, the system has been applied using different images and analyzing the results key space, key sensitivity, and statistical analysis and other criteria. From these tests, we can conclude that the encryption system can be used effectively to protect digital images