https://www.khanacademy.org/computing/computer-science/cryptography/crypt/v/intro-to-cryptography 2023-04-18T21:42:29.768102862Z What is cryptography? Cryptography has a rich history and plays a crucial role in modern communication networks. Learn about data encryption techniques through an example where Alice and Bob use secret codes (ciphers) to communicate privately. We'll learn about how encryption (locking messages) and decryption (unlocking messages) protect information from eavesdroppers like Eve.    Brit Cruise video https://cdn.kastatic.org/googleusercontent/CqAWCCyaRxvj3GfcWsDS_P-esRIiyL72aotktFxSohpP5eSdLsawhbPlIQlc5NYe1Q-qfoFA4BUWCI-F4oFlaX6PRg What is cryptography? Cryptography has a rich history and plays a crucial role in modern communication networks. Learn about data encryption techniques through an example where Alice and Bob use secret codes (ciphers) to communicate privately. We'll learn about how encryption (locking messages) and decryption (unlocking messages) protect information from eavesdroppers like Eve.    https://cdn.kastatic.org/ka-youtube-converted/Kf9KjCKmDcU.mp4/Kf9KjCKmDcU.mp4 91 Cryptography https://www.khanacademy.org/computing/computer-science/cryptography/crypt/v/perfect-secrecy 2021-03-22T14:52:38Z Perfect secrecy Claude Shannon's idea of perfect secrecy: no amount of computational power can help improve your ability to break the one-time pad Brit Cruise video https://cdn.kastatic.org/googleusercontent/oR19T86tK6rHScQUQvuYfV7wJdM2PO7TzvfZeQp5r5sO4TV95MhsvSTqgr7TvDHX-uaMMtHa5Od7xZ4xCN95psRppA Perfect secrecy Claude Shannon's idea of perfect secrecy: no amount of computational power can help improve your ability to break the one-time pad https://cdn.kastatic.org/ka-youtube-converted/vKRMWewGE9A.mp4/vKRMWewGE9A.mp4 253 Cryptography https://www.khanacademy.org/computing/computer-science/cryptography/crypt/v/polyalphabetic-cipher 2021-06-03T19:35:40Z Polyalphabetic cipher Brit introduces the polyalphabetic cipher, which creates a lighter fingerprint than the Caesar cipher. Brit Cruise video https://cdn.kastatic.org/googleusercontent/m1kwjAgwJ66x-39_i_Y4xauEIf8BE_sGlrOzUWsmf4I1wwiDRjIJo2ooEwRDK_-jT2vJdG_1DHtbdqJk7DbyBVKvSQ Polyalphabetic cipher Brit introduces the polyalphabetic cipher, which creates a lighter fingerprint than the Caesar cipher. https://cdn.kastatic.org/ka-youtube-converted/BgFJD7oCmDE.mp4/BgFJD7oCmDE.mp4 147 Cryptography https://www.khanacademy.org/computing/computer-science/cryptography/crypt/v/random-vs-pseudorandom-number-generators 2021-03-22T14:52:38Z Pseudorandom number generators Random vs. Pseudorandom Number Generators Brit Cruise video https://cdn.kastatic.org/googleusercontent/po8iWJVkEdYDt7gnDAF68_aJean5Fv-aWTf7A4vxRQ8oIkBiUQ1cGiSnvGNY2EpkqvQjb0tZX8cSvqgdwiA-NCZf Pseudorandom number generators Random vs. Pseudorandom Number Generators https://cdn.kastatic.org/ka-youtube-converted/GtOt7EBNEwQ.mp4/GtOt7EBNEwQ.mp4 401 Cryptography https://www.khanacademy.org/computing/computer-science/cryptography/crypt/v/caesar-cipher 2023-04-18T21:42:29.768102862Z The Caesar cipher The Caesar Cipher, used by Julius Caesar around 58 BC, is a substitution cipher that shifts letters in a message to make it unreadable if intercepted. To decrypt, the receiver reverses the shift. Arab mathematician Al-Kindi broke the Caesar Cipher using frequency analysis, which exploits patterns in letter frequencies. Brit Cruise video https://cdn.kastatic.org/googleusercontent/zYGRCWh5dppsV3Yr43IOtOp2U_JhdqgNmSXWbLXjXzuvA3EVzY6WAh8uOPqyK1lr11czN_tks3lGmSGdtlJWup8 The Caesar cipher The Caesar Cipher, used by Julius Caesar around 58 BC, is a substitution cipher that shifts letters in a message to make it unreadable if intercepted. To decrypt, the receiver reverses the shift. Arab mathematician Al-Kindi broke the Caesar Cipher using frequency analysis, which exploits patterns in letter frequencies. https://cdn.kastatic.org/ka-youtube-converted/sMOZf4GN3oc.mp4/sMOZf4GN3oc.mp4 157 Cryptography https://www.khanacademy.org/computing/computer-science/cryptography/crypt/pi/caesar-cipher-exploration 2022-09-10T01:34:41.474092194Z Caesar Cipher Exploration Type a message in the top box, then click and turn the wheel to encrypt it. interactive https://www.khanacademy.org/computing/computer-science/cryptography/modern-crypt/v/diffie-hellman-key-exchange-part-1 2023-04-18T21:42:29.768102862Z Public key cryptography: What is it? After WWII, the US and Soviet Union raced to become global superpowers, leading to the creation of NORAD and computer networking. As the internet grew, encryption became essential for secure communication. Diffie & Hellman devised a trick using one-way functions to share secret keys without eavesdroppers intercepting them. Brit Cruise video https://cdn.kastatic.org/googleusercontent/zQJWWF0G4dhmYhtYQHGm1zQoXsAyCZQEFVLZ-xwpy-vcYhA9oCjTsrbBllfhEOUJMbrwxpCUCn3EoT8UDrdcMCXq Public key cryptography: What is it? After WWII, the US and Soviet Union raced to become global superpowers, leading to the creation of NORAD and computer networking. As the internet grew, encryption became essential for secure communication. Diffie & Hellman devised a trick using one-way functions to share secret keys without eavesdroppers intercepting them. https://cdn.kastatic.org/ka-youtube-converted/MsqqpO9R5Hc.mp4/MsqqpO9R5Hc.mp4 272 Cryptography https://www.khanacademy.org/computing/computer-science/cryptography/cryptochallenge/e/clue-1-test 2026-04-08T00:36:09.500768563Z Crypto checkpoint 1 Test if you successfully decrypted clue 1, 2 & 3 brit cruise exercise https://www.khanacademy.org/computing/computer-science/cryptography/cryptochallenge/a/the-discovery 2025-07-16T20:19:55.489365237Z The discovery article https://www.khanacademy.org/computing/computer-science/cryptography/cryptochallenge/a/checkpoint 2021-04-29T07:50:14Z Checkpoint article https://www.khanacademy.org/computing/computer-science/cryptography/cryptochallenge/e/crypto-checkpoint-2 2026-04-07T22:59:30.107127435Z Crypto checkpoint 2 Test if you decrypted the secret code Nick exercise https://www.khanacademy.org/computing/computer-science/cryptography/cryptochallenge/e/crypto-checkpoint-3 2026-04-07T23:36:17.218592739Z Crypto checkpoint 3 Brit Cruise exercise