What is cryptography? (video) | Cryptography | Khan Academy
2021.03.17 13:45
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Courses Search Donate Login Sign up Search for courses, skills, and videos Main content Computing Computer science Cryptography Ancient cryptography
Ancient cryptography
What is cryptography? This is the currently selected item. The Caesar cipher Caesar Cipher Exploration Frequency Fingerprint Exploration Polyalphabetic cipher Polyalphabetic Exploration The one-time pad Perfect Secrecy Exploration Frequency stability property short film How uniform are you? The Enigma encryption machine Perfect secrecy Pseudorandom number generators Random Walk Exploration Next lesson Ciphers Current time: 0:00 Total duration: 1:31 0 energy points Computing · Computer science · Cryptography · Ancient cryptography
What is cryptography?
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Ancient cryptography
What is cryptography? This is the currently selected item. The Caesar cipher Caesar Cipher Exploration Frequency Fingerprint Exploration Polyalphabetic cipher Polyalphabetic Exploration The one-time pad Perfect Secrecy Exploration Frequency stability property short film How uniform are you? The Enigma encryption machine Perfect secrecy Pseudorandom number generators Random Walk Exploration Next lesson Ciphers
Video 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. The Caesar cipher Up Next The Caesar cipher
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