Abstract: One or more example embodiments include user terminals, methods, and/or computer-readable recording mediums storing computer programs, in which information encrypted or decrypted not to be decoded by a message server that controls transmission and reception of messages between one or more user terminals is not shared with the message server. One or more example embodiments include user terminals, methods, and/or computer-readable recording mediums storing computer programs, which encrypt a first message by using an encryption key, transmit the first message from a first user terminal to a second user terminal, and decrypt a second message received from the second user terminal by using the encryption key.

Abstract: One or more example embodiments include user terminals, methods, and/or computer-readable recording mediums storing computer programs, in which information encrypted or decrypted not to be decoded by a message server that controls transmission and reception of messages between one or more user terminals is not shared with the message server. One or more example embodiments include user terminals, methods, and/or computer-readable recording mediums storing computer programs, which encrypt a first message by using an encryption key, transmit the first message from a first user terminal to a second user terminal, and decrypt a second message received from the second user terminal by using the encryption key.

Abstract: One or more example embodiments include user terminals, methods, and/or computer-readable recording mediums storing computer programs, in which information encrypted or decrypted not to be decoded by a message server that controls transmission and reception of messages between one or more user terminals is not shared with the message server. One or more example embodiments include user terminals, methods, and/or computer-readable recording mediums storing computer programs, which encrypt a first message by using an encryption key, transmit the first message from a first user terminal to a second user terminal, and decrypt a second message received from the second user terminal by using the encryption key.

Abstract: A non-transitory computer-readable recording medium storing computer-readable instructions that, when executed by a first user terminal, cause the first user terminal to perform a method including: receiving a first message including a first attached file, generating at least one encryption key for encrypting the first message by taking into account a type of the first attached file, encrypting the first attached file of the first message by using the encryption key, adding sender information of the first message to the first message, and transmitting the first message including the sender information to a message server, may be provided.

Abstract: A non-transitory computer-readable recording medium storing computer-readable instructions that, when executed by a first user terminal, cause the first user terminal to perform a method including: receiving a first message including a first attached file, generating at least one encryption key for encrypting the first message by taking into account a type of the first attached file, encrypting the first attached file of the first message by using the encryption key, adding sender information of the first message to the first message, and transmitting the first message including the sender information to a message server, may be provided.