Homomorphic Ciphertext Transformation for Reduced A-Part Storage
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Solution Overview
Problem
Homomorphic encryption ciphertexts are significantly larger in size compared to plaintext, requiring substantial storage space, especially in database environments, and existing methods do not effectively reduce this size.
Innovation Solution
An electronic apparatus and method that transform homomorphic ciphertexts using a first scheme into a second scheme by iteratively performing partial transformation operations, merging ciphertexts with shared a-parts and different b-parts, and applying modulus expansion and linear transformations to reduce the dimension and size of the a-part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If homomorphic encryption is used to encrypt data, then security is improved, but ciphertext size increases significantly
Solution Approach 1:
The patent merges multiple ciphertexts that share the same a-part into a single aggregated ciphertext. By combining k ciphertexts (c1, c2, ..., ck) that have identical a-parts into one aggregated ciphertext containing the sum of their b-parts, the storage requirement is reduced from k separate ciphertexts to one, directly addressing the ciphertext size problem while maintaining security through homomorphic properties
Solution Approach 2:
The patent creates a universal a-part that can be shared across multiple ciphertexts. Instead of generating unique a-parts for each ciphertext, the same a-part is reused universally across k different ciphertexts, reducing redundancy and storage overhead while preserving the security and functionality of individual ciphertexts
2Adaptability or versatility
If multiple homomorphic ciphertexts are stored in a database, then data availability is improved, but storage space requirement increases
Solution Approach 1:
The patent applies merging by aggregating multiple ciphertexts into a single stored entity. When k ciphertexts with shared a-parts need to be stored, only one aggregated ciphertext is stored in the database, reducing storage space from O(k) to O(1) for the a-part component while maintaining data availability through the homomorphic structure
Solution Approach 2:
The patent discards redundant a-parts that would otherwise be stored multiple times. Since the a-part is identical across k ciphertexts, it is stored once and then recovered/reused when needed for decryption or operations, eliminating redundant storage while preserving data accessibility
3Adaptability or versatility
If conventional homomorphic ciphertext format is used, then encryption flexibility is maintained, but processing efficiency decreases
Solution Approach 1:
The patent improves processing efficiency by merging operations on multiple ciphertexts into a single aggregated operation. Instead of processing k separate ciphertexts individually, the system performs one aggregation operation followed by a single decryption, reducing computational overhead and improving processing throughput while maintaining encryption flexibility
Solution Approach 2:
The patent segments the ciphertext structure into two independent components: a shared a-part and individual b-parts. This segmentation allows the a-part to be processed once for multiple ciphertexts while b-parts are handled individually, improving processing efficiency by eliminating redundant operations on the a-part component
Data Source
AI summary
An electronic apparatus includes: a memory for storing an instruction; and a processor configured to execute the instruction to thus transform a first homomorphic ciphertext homomorphically encrypted using a first scheme into a second homomorphic ciphertext encrypted using a second scheme, wherein each of the first homomorphic ciphertext and the second homomorphic ciphertext includes an a-part and a b-part, the first scheme is a homomorphic ciphertext format in which a plurality of homomorphic ciphertexts have different a-parts and b-parts, the second scheme is a homomorphic ciphertext format in which a plurality of homomorphic ciphertexts have the same a-part and only different b-parts, and the processor is configured to transform the first homomorphic ciphertext into the second homomorphic ciphertext by iterating a partial transformation operation of gradually increasing a rank of a secret key multiple times.