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Cryptography · Module 1 of 10

Introduction to cryptography

Cryptography protects information with mathematics.

📖 Key ideas

  1. Cryptography keeps data confidential, intact and authentic.
  2. Plaintext is readable; ciphertext is scrambled.
  3. Encryption uses a key; decryption reverses it with a key.
  4. Kerckhoffs's principle: security should rely on the key, not on hiding the algorithm.
  5. Used in HTTPS, UPI, WhatsApp, banking and passwords.
💡 Real-life example: Cryptography is a lockbox: anyone can know how the lock works, but only the key holder can open it.
PlaintextReadable data
CiphertextEncrypted data
KeySecret value used by an algorithm
Kerckhoffs's principleSecurity depends on the key, not secrecy of the method