Teach encryption, public and private keys, and digital certificates with a 78-slide IB Computer Science SL & HL presentation for A2.4.4, first assessment 2027.

Help students explain how encryption protects data and how digital certificates establish trust in secure network connections. Visual explanations, applied scenarios and checkpoints support teaching and revision.

Topics covered

• Plaintext, ciphertext, encryption and decryption
• Encryption keys and the role of algorithms
• Symmetric encryption and the shared-key distribution problem
• Asymmetric encryption and public/private keys
• Symmetric versus asymmetric encryption comparisons
• Hybrid encryption and secure key establishment
• Digital certificates and certificate authorities
• Digital certificates versus digital signatures
• HTTPS and SSH examples
• Secure key management: creation, distribution, usage, storage, retirement and deletion
• Diffie–Hellman key exchange as enrichment

Teaching and revision activities

• Learning objectives and a secret-message starter
• Visual workflows and practical examples
• Checkpoints and applied scenario tasks
• IB-style practice questions with suggested answers
• Exam technique: key terms and common mistakes
• Two-part exit ticket with 18 questions and model answers