Partial Private Key Segmentation for Identity-Based Encryption
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Solution Overview
Problem
Identity-based encryption systems face the key escrow problem, where the trusted center has access to all private keys, making them vulnerable to attacks if the master key is compromised, and lacking forward secrecy and message confidentiality.
Innovation Solution
The system implements partial private keys for users, allowing secure message exchange without relying on the trusted center for decryption, ensuring forward secrecy and protecting messages from master key corruption by using partial private keys and public session keys for encryption and decryption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a trusted center generates and manages all private keys in an identity-based encryption system, then key distribution and user authentication are simplified, but the system becomes vulnerable to key escrow attacks and loses forward secrecy
Solution Approach 1:
The private key is segmented into two parts: a partial private key generated by the trusted center and a user-specific secret key generated by the user. This segmentation allows the trusted center to facilitate key distribution while preventing it from having access to the complete private key, thus resolving the key escrow vulnerability while maintaining operational simplicity.
Solution Approach 2:
Different parts of the key generation process have different security requirements. The trusted center generates the partial private key with controlled knowledge, while the user generates their own secret key component that remains private. This local differentiation of key generation responsibilities maintains ease of operation while ensuring message confidentiality.
2Ease of operation
If the trusted center has access to all private keys for authentication purposes, then user verification is centralized and simplified, but the system lacks forward secrecy when the master key is compromised
Solution Approach 1:
By segmenting the private key into a trusted center-generated partial key and a user-generated secret key, the system maintains centralized authentication capability while ensuring that compromise of the trusted center's master key does not reveal user-specific secret keys, thereby preserving forward secrecy.
Solution Approach 2:
The partial private key acts as an intermediary that enables the trusted center to perform authentication functions without having access to the complete private key. This intermediary mechanism allows centralized user verification while protecting against master key compromise affecting past communications.
3Device complexity
If complete private keys are stored at the trusted center for all users, then key management is centralized, but the system becomes vulnerable to attacks if the master key is compromised
Solution Approach 1:
The private key is divided into a partial private key managed by the trusted center and a secret key held by the user. This segmentation maintains centralized key management structure while eliminating the vulnerability associated with storing complete private keys at the trusted center, as the user's secret key component cannot be derived from the trusted center's data.
Solution Approach 2:
The vulnerable element (complete private key storage at trusted center) is extracted and replaced with a partial private key. The user's secret key component is taken out from the trusted center's control and kept locally, thereby removing the attack vulnerability while preserving key management functionality.
Data Source
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AI summary
A transmitter device (103) for sending an encrypted message to a receiver device (105) in an identity-based cryptosystem (100), the transmitter device (103) being associated with a transmitter identifier. The transmitter device (103) is configured to receive a transmitter partial private key from a trusted center (101), the transmitter device (103) being configured to: - send a request for two public session keys to the receiver device (105); - receive from the receiver device (105) a first ciphertext set, the first ciphertext set being derived from an encryption and authentication of two public session keys; - decrypt and authenticate the two public session keys from the first ciphertext set using a receiver identifier and the transmitter partial private key; - determine a second ciphertext set from the transmitter partial private key, from the receiver identifier, and from the two public session keys, the second ciphertext comprising an encrypted message; - send the second ciphertext set to the receiver device (105).