Secure Message Encryption and Decryption with Encryption Hardware
Alice and Bob have agreed a symmetric key to be used for encrypting messages to be sent over an insecure communication channel. Both of them have hardware devices for carrying out the encryption, but no decrypting tools. In this article, we will explore how to design a scheme for secure message encryption and decryption using only encryption hardware.
Designing the Scheme
One possible solution is to use the XOR operation. XOR is symmetrical, meaning that if you apply a XOR k XOR k, you obtain a again. This property makes XOR suitable for encryption and decryption using the same key. To encrypt a message, you can simply perform an XOR operation between the message and the encryption key. And to decrypt the message, you can perform another XOR operation between the encrypted message and the same encryption key.
By using this scheme, Alice can encrypt a message using her encryption hardware and send it to Bob. Bob can then use his encryption hardware to decrypt the message and retrieve the original content. This ensures privacy and security even without the need for decrypting tools.