Communication system, first communication device, second communication device, communication method

Abstract

[Problem] To provide a technique that enables two communication devices engaged in encrypted communication to securely and easily share data. [Solution] A first communication device encrypts the shared data using a first decryption and its inherent first key to generate first encrypted data (step S503), and transmits it to a second communication device (step S504). The second communication device receives this data (step S601), decrypts the first encrypted data using the first decryption, and encrypts it using a second decryption and its inherent second key to generate second first encrypted data (step S602), and transmits it to the first communication device (step S603). The first communication device receives this data (step S505), decrypts the second first encrypted data using the first key, and encrypts it using a third decryption to generate second encrypted data (step S506), and transmits it to the second communication device (step S507). The second communication device receives this data (step S604), decrypts the second encrypted data using the third decryption and the second key to return the shared data (step S605).

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