About this video
Alice and Bob want to share a secret while Eve tries to intercept their messages. Locking a message in a box with a shared combination is like encryption, and opening it with the shared code is decryption. Cryptography replaces physical locks with ciphers, virtual locks that scramble messages so they look meaningless to an eavesdropper.
You'll be able to
- explain the difference between encryption and decryption.
- describe what a cipher does.
- explain why cryptography matters for communication.
Key words
- eavesdropper
- Someone who secretly listens in on or intercepts messages, like Eve.
- encryption
- Locking or scrambling a message so only people with the key can read it.
- decryption
- Unlocking or unscrambling a message using the shared key.
- cipher
- A virtual lock: a method for scrambling and descrambling messages.
- cryptography
- The study and use of ciphers to keep messages secret.
Transcript
Imagine two people who share an important secret have to split up. This requires them to communicate private information from a distance. However, an eavesdropper named Eve also wants this information, and has the ability to intercept their messages. So, Alice decides to communicate using letters written in some kind of secret code.
The following analogy is helpful. First, Alice locks her message in a box, using a lock that only she and Bob know the combination to. This is known as 'encryption.' Then, the locked message is sent to Bob. When Bob receives the box, he opens it using the code they shared in advance.
This is called 'decryption.' Cryptography begins when we abandon physical locks and use 'ciphers' instead. Think of [ciphers] as virtual locks. Ciphers allow Alice and Bob to scramble and descramble their messages so that they would appear meaningless if Eve intercepted them.
Cryptography has been around for thousands of years. It has decided wars, and is at the heart of the worldwide communication network today. The fascinating story of cryptography requires us to understand two very old ideas related to number theory and probability theory.
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