Method and device for exchanging key

A method for acquiring a key, the method being performed by a second communication device related to a second user, the method comprising:

• receiving a second public key and encrypted first data from a first communication device related to a first user;
• decrypting the encrypted first data using a first secret key generated based on an identifier of the second user;
• acquiring a first public key based on an identifier of the first user;
• encrypting second data using the first public key;
• encrypting third data using the second public key;
• transmitting the encrypted second data and the encrypted third data to the first communication device such that the first communication device generates a session key;
• and
• generating the session key using the decrypted first data, the decrypted second data, and the decrypted third data.

A computing device comprising:

• one or more processors;
• and
• a memory for storing therein a computer program executed by the one or more processors,
• wherein the computer program includes instructions for:
• acquiring a first public key using an identifier of a second user;
• encrypting first data using the first public key;
• transmitting a second public key and the encrypted first data to a communication device related to the second user;
• receiving encrypted second data and encrypted third data from the communication device;
• decrypting the encrypted second data using a first secret key generated based on an identifier of a first user;
• decrypting the third data using a second secret key related to the second public key;
• and
• generating a session key for communication with the communication device, using the decrypted first data, the decrypted second data, and the decrypted third data.