With the rapid development of cloud computing, an increasing volume of sensitive data is being outsourced to external servers in encrypted form. However, performing efficient full-text searches over encrypted data without compromising privacy remains a major challenge. Existing searchable symmetric encryption (SSE) schemes are primarily designed for structured data and lack support for full-text search capabilities. To address this limitation, we propose a novel SSE scheme that enables full-text substring search over ciphertext without requiring any preconstructed indexes. The proposed approach integrates dynamic key generation with a Bloom filter–based query matching mechanism, allowing secure and efficient substring search directly on encrypted data. This design enables encrypted documents to be queried without revealing their content or structural information. Security analysis and experimental evaluations demonstrate the practicality of the proposed scheme and its strong resistance to statistical and pattern-based attacks. These properties make the scheme well-suited for trust-aware applications in cloud computing, the Internet of Things (IoT), and social networking environments.