AP CSP Day 21: Encryption & Security Tradeoffs
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Encryption transforms readable data (plaintext) into an unreadable format (ciphertext) using a key, protecting it from unauthorized access during transmission or storage. Public key cryptography uses a public key to encrypt and a private key to decrypt, enabling secure communication without sharing a secret key in advance. AP CSP exam questions about encryption often ask students to identify what encryption protects against and what it does not. A key tradeoff is that stronger encryption improves security but requires more computational resources.
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Encryption and Security Tradeoffs
What Is Encryption?
Encryption transforms readable plaintext into unreadable ciphertext using a mathematical algorithm and a key. Only someone with the correct key can decrypt the ciphertext back into plaintext. Encryption protects data confidentiality during transmission and storage.
Symmetric vs. Public Key
Symmetric encryption uses the same key to encrypt and decrypt, which is fast but requires the key to be shared securely beforehand. Public key (asymmetric) encryption uses a public key to encrypt and a private key to decrypt, solving the key-sharing problem.
Practice Question
A website uses HTTPS instead of HTTP. Which of the following best describes what HTTPS provides?
HTTPS uses TLS/SSL encryption to protect data during transmission between the browser and server. This prevents third parties from reading or tampering with the data while it travels across the network.
A) HTTPS can add slight overhead due to encryption processing; it does not make sites faster. C) HTTPS secures the communication channel but does not scan or prevent malware on the site itself. D) HTTPS protects data in transit — it says nothing about the truthfulness or accuracy of the website's content.
Students think the padlock icon (HTTPS) means a website is completely safe or trustworthy. HTTPS only protects data in transit — it does not verify content quality or prevent all security threats.
HTTPS = encrypted connection. It protects data IN TRANSIT only. A malicious website can still use HTTPS. Do not equate HTTPS with overall website safety.
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