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PlayOwl

Computers & Digital Literacy · Grade 9

Cryptography Concepts without Real Secrets

Using only toy examples, learners build the vocabulary of cryptography with a shift cipher and see why its tiny key space makes it useless for real secrets. They compare shared-key and public-key encryption, explore hashing with a deliberately weak toy hash, and finish with digital signatures, certificates, what the browser padlock really means, and good key-management habits.

  • 4 lessons
  • About 110 minutes
  • Cryptography concepts check: 10 questions
  • Ways to answer: fill in the blanks, choose an answer, trace code, highlight a text, match pairs and type a number
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What learners will discover

  • Use the vocabulary of encryption (plaintext, ciphertext, algorithm, key) with a toy shift cipher, and explain why a small key space makes a cipher insecure.
  • Compare shared-key (symmetric) and public-key (asymmetric) encryption, including the key-sharing problem and which key is used for encrypting and for signing.
  • Explain the properties of hash functions and how hashes support integrity checks and safe password storage with salts.
  • Explain digital signatures, certificates and the meaning of the browser padlock, and choose good key-management practices.

Lessons

  1. Ciphers, keys and key space 7 steps4 practiceabout 30 min
  2. Shared keys and public keys 7 steps4 practiceabout 30 min
  3. Hashing: fingerprints for data 8 steps5 practiceabout 25 min
  4. Signatures, certificates and key management 5 steps2 practiceabout 25 min
  5. Cryptography concepts check 10 questions at the end

Keep exploring

More 9th grade computer skills

Guide for grown-ups