Abstract: A document storage system enables users to send documents received from third-party document providers to a secure vault and subsequently allow the users to provide stored documents to receiving entities in a manner that guarantees that the provided documents have not been modified. Responsive to receiving a user request for a specified document, a providing entity automatically sends the requested document to the document storage system, along with metadata representative of the document, the user, and the providing entity. The document storage system generates a first document fingerprint using the received metadata and stores the document and fingerprint in the vault. When a user requests to share the stored document with a receiving entity, the document storage system generates a second document fingerprint based on document metadata stored in the vault and sends the document and first and second fingerprints to the receiving entity.