Took assessment on algebra review topics.
Homework:
do any missing HW required to utilize re-assessment day in class this week and next week
Click Read More to see the Online Cryptanalysis Challenge!!!
For over 400 years, the Vigenère Cipher remained virtually unbreakable, and secrets of all kinds were securely transmitted using it. With a very long key phrase, it can be still be considered unbreakable, particularly if the key phrase is the same length of the message.
Cracking the Vigenère Cipher was a landmark achievement in the history of mathematics, linguistics, and even early computer science. It uses something called "Frequency Analysis" which concerns the usage of letters in the English language. The most commonly used letters are ETAOIN SHRDLU
1. Read over this page on how the Vigenere Cryptanalysis works.
2. Choose/type a suitably long plaintext message to encode as well as a keyword keyphrase. Encode it using this tool and post your message in the comments below.
3. Find a classmate's comment to decode. Copy and paste their text into this tool and follow the instructions on the page. If you are confused by the instructions, check out this video (use headphones to listen if possible). Some tips: Look for the 3 peaks at A, E, and I (each separate by 3 lower frequency characters). Normally if this lines up, the rest of the alphabet does as well and you have determined a letter of the code. If the tool is not working or is taken down, try these alternatives: [1] [2]
4. If you use the tool from step 3 properly, then you should have determined the key word. Paste the ciphertext into this tool and enter the keyword and decode it. You should be able to see a readable message! Words might be broken apart, but read between the lines and you should see proper English text.