Encrypted Message Search via Dynamic Salt Hashing
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Solution Overview
Problem
Current cloud-based message transmission/reception systems are insufficient in protecting against server threats, such as cyber-attacks and internal unauthorized access, as existing methods for encrypting messages stored on servers can still lead to leakage if decryption is possible, and techniques for searching encrypted messages without decryption are vulnerable to guessing the search content and results.
Innovation Solution
An encrypted message search method where terminals share a session key and generate a random search secret key, encrypt it, and update it periodically, allowing the server to search for encrypted messages without decrypting them, using a room identifier and index sets to manage and retrieve messages securely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If messages are encrypted and stored on the server, then security against terminal threats is improved, but the ability to search messages without decryption deteriorates
Solution Approach 1:
The message data is segmented into two separate components: encrypted message content (ciphertext) and searchable index data. The index is generated by applying a hash function to the plaintext message and is stored separately from the encrypted content. This segmentation allows the server to search the index without accessing or decrypting the actual message content, resolving the contradiction between security and searchability.
Solution Approach 2:
A hash-based index acts as an intermediary between the search query and the encrypted message storage. When a search is performed, the system hashes the search term and compares it against the index rather than decrypting and scanning message content. This intermediary mechanism enables efficient search operations while maintaining end-to-end encryption of the actual messages.
2Ease of operation
If a hash value is recorded for encrypted data search, then search capability is improved, but vulnerability to guessing attacks using rainbow tables worsens
Solution Approach 1:
The system implements dynamic salt values that are generated and updated periodically or per message. These salt values are combined with the original message content before hashing, creating a dynamic hashing process. This ensures that even identical messages produce different hash values over time, preventing attackers from using static rainbow tables to guess message content, while still maintaining efficient search capability through the updated index.
Solution Approach 2:
The hashing process parameters are changed by introducing and updating salt values. The salt acts as an additional parameter that modifies the hash function's behavior, ensuring that the same input message produces different hash outputs at different times or under different conditions. This parameter change strategy secures the hashing mechanism against rainbow table attacks while preserving search functionality.
3Reliability
If session keys are shared among terminals for end-to-end encryption, then security against server wiretapping is improved, but the complexity of key distribution and management worsens
Solution Approach 1:
The system extracts the key distribution problem from the overall encryption system by using asymmetric cryptography (public-key infrastructure). Each terminal generates a key pair, and only the public key needs to be shared among group members. The private key remains securely stored in each terminal. This extraction approach simplifies key distribution compared to symmetric key exchange, as public keys can be freely shared without compromising security, while still achieving end-to-end encryption.
Solution Approach 2:
The public key serves multiple functions: it enables other terminals to encrypt messages intended for the private key holder, it can be used to verify digital signatures, and it facilitates secure key exchange. This multi-functionality reduces the overall key management complexity by consolidating multiple cryptographic needs into a single key pair mechanism.
Data Source
AI summary
There is provided an encrypted message search technique making it difficult to, at the time of searching for a message in a state of being encrypted, guess content of the search and a result of the search. There are included: an encrypted search secret key transmission step of a terminal generating an encrypted search secret key from a search secret key generated each time an update interval set in advance elapses and transmitting the encrypted search secret key to a server; a search secret key decryption step of the terminal decrypting the encrypted search secret key acquired from the server to obtain the search secret key; an encrypted message transmission step of the terminal transmitting an index set generated using information related to a message and a newest search secret key, and an encrypted message to the server; a query transmission step of the terminal transmitting a query set generated using a message search character string and the search secret key; and an encrypted message returning step of the server transmitting an encrypted message including elements of an index set corresponding to an element of the query set.