Third-party-based safety file storage and sharing system and method

The invention discloses a third-party-based safety file storage and sharing system and method. With the system and method, encrypted file uploading, file downloading and decryption, safety file storage to a third party, and safety sharing of a file in a system are realized. According to the invention, file encryption and decryption at a user terminal is realized. Decryption is carried out on a file secret key at a user terminal and then encryption is carried out again by using an opposite-party public key to generate a new file secret key; the file secret key is uploaded to a server side for storage; a shared file mark is made in a file list of a shared file receiver; and when the shared file receiver needs to obtain a shared file, the file secret key is decrypted by using a private key and then the file is decrypted, thereby obtaining a final file. Therefore, file safety in a sharing system can be guaranteed; and complexity of a sharing method of ciphertext files is reduced. The system calculated amount is reduced fundamentally. With the secret key distribution way, the user only has the control permission on own files, so that file storage becomes safe.