Abstract: Method, apparatus and system for data encryption and decryption. In an embodiment, the method comprises: generating a block key and encrypting to-be-uploaded data based on the block key to obtain encrypted data; encrypting the block key based on a public key of a preset target object to obtain an encrypted block key corresponding to the preset target object; generating upload data based on the encrypted data and the encrypted block key, and uploading the upload data to a blockchain.

Abstract: In a message processing method and device described in the disclosed embodiments, a sender sends to a receiver a message in a read-only mode; the receiver displays content of the message in the read-only mode to a user; because the message is in the read-only mode, the receiver cannot store the message; the sender clears the content of the message and sends to the receiver the message with null content; the receiver again receives the message and updates displayed content of the message with content of the most recently received message; because the content of the message is already cleared at the sender, the content displayed at the receiver is also empty, thereby achieving the deletion of the message content. It can be appreciated that through the disclosed methods and devices, it can be guaranteed that both the message content being deleted at the receiver and the message not being stored by the receiver, thereby reducing the risk that the message content may be retained by the receiver.