What Everyone Needs to Know Q&A: As the worldwide issue of cybersecurity prevails, companies such as IBM are trying to facilitate the encryption of data on a massive scale. To battle hackers and protect our information, we want to know:

Can quantum physics be harnessed to create perfectly secure Internet communication?

Yes. In recent decades scientists have learned how to use the quantum nature of light to make messages and other data almost perfectly secure. Quantum physics allows us to encrypt messages in ways that cannot be cracked by any computing method in a reasonable amount of time. Data encryption using quantum techniques is an excellent topic for our first foray into technological applications of quantum physics.

How does encryption keep messages secret?

For financial, industrial, military, or personal reasons, people often want to send messages so that only the sender and intended recipient can know its contents. Typically, encryption systems use some kind of ‘replacement system,’ in which letters or numbers are replaced by other letters, numbers, or symbols according to some preset, but secret, rule. The more complex the rule, the harder the system is to crack.

The art of sending messages in secret has a history going back many centuries. In ancient times, Julius Caesar used a system, now called the Caesar Cipher, in which each letter of the alphabet was replaced by the letter appearing some fixed number of positions later in the alphabet (and starting over at the beginning when the alphabet’s end is reached). The fixed number is called the encryption key, because it is used to ‘lock’ and ‘unlock’ the encrypted text. For example, if the key equals 2, the text, “I love you” would be replaced by “K nqxg aqw.” The recipient, if he knows the key equals 2, can easily reverse, or decipher, the encryption process by shifting each letter back by two positions in the alphabet. If the key is known only to the sender and the intended recipient, it is called a secret key. A third person, lacking the key, will have a tough time deciphering the message.

[Page 54-55, Quantum Physics: What Everyone Needs to Know by Michael G. Raymer]