Pioneering Public Key: Public Exchange of Secret Keys
- The Search for an Innovative Key Delivery Solution
- Developing an Innovative Secret Key Delivery Solution
- A New Solution: Diffie-Hellman-Merkle Key Agreement
- Separate Encryption and Decryption Keys
Let's recap and lay the groundwork to see how a new twist on secret key distribution empowers a new form of cryptography.
Alice and Bob have developed secure secret keys. Alice encrypts her computer files and feels secure that no one can decrypt the files without her individual secret key. Alice and Bob's digital conversations use their shared secret key to authenticate each other, confidentially exchange files, and validate the integrity of the files (ensure that the files have not been altered during transit).
|Review: Sharing and distributing secret keys is cumbersome.|
But as you saw in Chapter 8, sharing secret keys is difficult and expensive. Alice must either personally deliver the shared secret key to Bob or unequivocally trust a courier. Trustworthy couriers are expensive. And if Bob forgets their shared secret key, Alice must repeat the same key delivery process.
The secret key delivery problem has plagued cryptographers, governments, and kings for thousands of years. How do you securely deliver a secret key to a confidant using insecure public lines of communication? Although the key may pass through BlackHat's hands, BlackHat must not be able to ascertain the secret key. It's a tough problem. What advantage does Bob have over BlackHat that Bob can exploit?