A Secure Document Secret Sharing System using SHA-256-based Share Authentication

In today's digital world, ensuring the confidentiality and secure transmission of sensitive documents has become increasingly crucial. This paper presents the design and implementation of a Document Secret Sharing (DSS) system based on Shamir's (k,n) Secret Sharing Scheme, integrated with SHA-256 based share authentication. Unlike existing verifiable secret sharing (VSS) systems, this work applies secret sharing at the document level and incorporates hash-based verification to ensure integrity. The system divides a document into multiple independent shares such that any k (e.g., (3,5), (4,6), (5,8)) are sufficient for reconstruction, while fewer reveal no information. The implementation is carried out using Python and includes a user-friendly graphical interface developed with Tkinter, allowing users to effortlessly generate shares. Furthermore, each share is individually authenticated using SHA-256, a hash function, to detect tampering and ensure data integrity during transmission. Experimental results demonstrate reliable integrity preservation with negligible overhead (3- 5% share size increase) and reconstruction times under 2 seconds for files up to 5 MB. The proposed DSS approach provides a practical, secure, and efficient solution for confidential document sharing and lays the groundwork for future research in secure data collaboration.