XOR-Homomorphic Ciphertext Search System
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Solution Overview
Problem
Conventional encryption methods, such as AES, do not support searching functionality on encrypted data, making them unsuitable for outsourcing data management to untrusted servers, and existing solutions like DET, OPE, and HOM face issues like data leakage and high computational complexity.
Innovation Solution
A method and system using an exclusive-or (xor) homomorphic function to generate and decrypt ciphertexts, allowing for secure searching by randomizing encrypted data with a cipher pad generated based on an xor-homomorphic function, which preserves data structure and prevents access pattern leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional encryption methods (AES) are used to ensure data confidentiality, then data security is improved, but searching functionality on encrypted data is lost
Solution Approach 1:
The encryption process is segmented into two distinct stages: first, deterministic encryption is applied to enable searching functionality; second, randomization is applied to restore confidentiality. This segmentation allows each stage to fulfill its specific function without compromising the other, resolving the contradiction between searchability and security.
Solution Approach 2:
A randomization layer acts as an intermediary between deterministic encryption and the external environment. This intermediary preserves the structured properties needed for searching while hiding the actual data patterns from observers, thus maintaining both searchability and confidentiality simultaneously.
2Ease of operation
If deterministic encryption (DET) is used to support equality checking on encrypted data, then searching functionality is improved, but access patterns are leaked
Solution Approach 1:
The randomization layer serves as an intermediary that masks the deterministic ciphertext patterns. By applying random noise to the encrypted data, the system preserves the ability to perform equality checks while concealing the access patterns that would otherwise be visible to external observers.
Solution Approach 2:
The system changes the parameter of the encrypted data from a fixed deterministic form to a randomized form. This parameter change allows the data to maintain its searchability properties while altering its observable characteristics to prevent access pattern leakage.
3Ease of operation
If order-preserving encryption (OPE) is used to support range checking on encrypted data, then searching functionality is improved, but data order is leaked
Solution Approach 1:
The randomization layer acts as an intermediary that preserves the order relationships needed for range queries while masking the actual data values. The randomized ciphertext maintains the relative ordering properties necessary for OPE functionality but hides the underlying data distribution and order patterns.
4Reliability
If homomorphic encryption (HOM) is used to support secure data updates, then data security is improved, but computational complexity becomes too high
Solution Approach 1:
The cryptographic functionality is segmented into simpler, more efficient components: deterministic encryption for structural preservation and lightweight randomization for security. This segmentation avoids the need for computationally intensive homomorphic encryption while achieving similar security goals with much lower complexity.
Solution Approach 2:
The system uses computationally inexpensive encryption and randomization operations instead of expensive homomorphic encryption. These lighter cryptographic primitives achieve the necessary security properties without the high computational overhead of full homomorphic encryption schemes.
Data Source
AI summary
There is provided a method of generating a ciphertext. The method includes encrypting an input data to produce an encrypted data, and randomizing the encrypted data to produce the ciphertext. In particular, the randomizing process includes performing an exclusive-or (xor) operation on the encrypted data with a cipher pad, whereby the cipher pad is generated based on an xor-homomorphic function of a first key using a second key generated based on the encrypted data. There is also provided a corresponding system for generating a ciphertext, a corresponding method and system for decrypting a ciphertext, and a corresponding method and system for searching ciphertexts in a database, such as at an untrusted server.