One of the biggest workhorses in [[Encryption|encryption]] schemes are [[Symmetric Encryption|symmetric encryption]] algorithms: both parties know the same key and use it to encrypt or decrypt a message. Famous examples are schemes like the [[Vignere Cipher|Vignere cipher]] or the [[Ceasar Cipher|Caesar chipher]]. The main weakness of [[Symmetric Encryption|symmetric encryption]] methods is the key exchange. How do two parties get to know the same secret without anyone else knowing it? Here are some options: - The two parties could meet and make sure not be overheard while exchanging the secret. While this works on a small scale (few parties, short distances), it quickly gets difficult if the parties are far removed or there are many (think about the number of devices on the Internet). - Alternatively, the two parties could use a trusted envoy. However, that envoy might be bribed or the secret could be stolen from them. - Today, many systems that need to communicate over an encrypted line use key exchange algorithms like the [[Diffie-Hellman Key Exchange|Diffie-Hellmann key exchange]]. While this schemes are considered hard to break with classical computers, certain [[Quantum Algorithm|quantum algorithms]] like the [[Shor Algorithm|Shor algorithm]] make them susceptible to attack. - One method, based on [[Quantum Technologies|quantum technologies]], is [[Quantum Key Distribution|quantum key distribution algorithms]]. These algorithms use features of [[Quantum Mechanics|quantum mechanics]] to ensure that information cannot be copied during the transmission. While these protocols are secure in theory, there are still options to attack the hardware implementation. >[!read]- Further Reading >- [[Quantum Key Distribution]] >- [[Quantum Mechanics]] >- [[No-Cloning Theorem]] >[!ref]- References