Group message sending method and system, group message receiving method and system and communication terminal

The invention discloses a group message sending method and system, a group message receiving method and system and a communication terminal. The group message sending method comprises the steps of taking a time stamp, an interaction key and a key seed corresponding to a local group as input, carrying out operation through a preset key generation algorithm and generating a current message key; encrypting a current group message through utilization of the current message key and a preset symmetric encryption algorithm, thereby obtaining a ciphertext message; and sending the ciphertext message and the corresponding time stamp to other client modules in the local group through a group chat message platform. According to the methods, the systems and the communication terminal, the current message key can be updated in real time, so the risk that the current message key is broken can be effectively reduced. Even if other person obtains the preset key generation algorithm, data transmission is not carried out on the key seed along with the ciphertext message, so the other person is difficult to obtain the key seed, under the condition that the key seed cannot be obtained, the other personcannot obtain the current message key, and the ciphertext message cannot be decrypted.