Policy Hiding in Ciphertext-Policy Attribute-Based Encryption

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Solution Overview

Problem

In ciphertext-policy attribute-based encryption (CP-ABE) systems, sensitive information about access policies is disclosed to third parties, revealing which attributes or groups can decrypt the ciphertext, compromising confidentiality.

Innovation Solution

The method involves categorizing attributes into groups with common attributes, using a group-based attribute set to hide sensitive policy portions, and converting AND subtrees into sub-ciphers, allowing only those with the common attribute to decrypt, thereby masking the policy details.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If access tree structure is used in CP-ABE to enable fine-grained access control, then decryption capability is improved, but policy information leakage occurs revealing sensitive attribute requirements

Engineering Contradiction:

Improveaccess control capabilityVSAvoidpolicy confidentiality

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The access tree is segmented into multiple subtrees, where each subtree is encrypted independently using a different branch of the attribute hierarchy. This segmentation allows the system to hide the complete access policy structure while still enabling fine-grained access control through the individual encrypted subtrees.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Encrypted subtrees act as intermediaries between the access policy and the decryption process. Instead of exposing the raw access tree structure, the system uses these encrypted representations to mediate access control, allowing authorized users to decrypt without revealing the underlying policy details to third parties.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If specific attributes are exposed in ciphertext to enable decryption verification, then decryption accuracy is improved, but sensitive policy details are disclosed to third parties

Engineering Contradiction:

Improvedecryption verification accuracyVSAvoidpolicy information disclosure

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Different parts of the access tree are treated with different levels of encryption. Specific subtrees are encrypted while others remain in plaintext, allowing the system to maintain decryption verification accuracy for essential attributes while protecting sensitive policy portions through localized encryption applied selectively to specific tree segments.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11316662B2Method and apparatus for policy hiding on ciphertext-policy attribute-based encryption

Publication Date: 2022.04.26 KONINKLIJKE PHILIPS NV

AI summary

Various embodiments relate to a method and apparatus for policy-hiding on ciphertext-policy attribute based encryption, the method including the steps of categorizing each of a plurality of attributes into a plurality of groups where each of the plurality of groups has a group attribute, inputting a policy and a message into an encryption algorithm and outputting a ciphertext; and encrypting an AND subtree in the policy and outputting a sub-cipher.