← VCE Cyber Security

Asymmetric encryption

Encryption that uses a linked pair of keys: a public key to encrypt data and a private key to decrypt it, with no shared secret key needed.

Part of: VCE Applied Computing - U2O2 - Cyber Security — Module 49, VCE Software Development - U4O2 - Cyber Security: secure software development practices — Module 59, VCE Data Analytics - U4O2 - Cyber Security: Data Security — Module 69, IGCSE Computer Science 0478 — 2.3 Encryption — Module 13, ACARA Digital Technologies Years 7–8 — Networks and Cyber Threats — Module 65, ACARA Digital Technologies Years 9–10 — Networked Systems and Access Control — Module 82, ACARA Digital Technologies Years 9–10 — Cyber Security Threats and Vulnerabilities — Module 136, QCE Digital Solutions Unit 4 — Digital Methods for Exchanging Data — Module 30, WA Computer Science ATAR Year 11 — Cyber Security — Module 78

Understanding Asymmetric encryption in VCE Cyber Security

What it does: This code generates the linked public and private keys used for asymmetric encryption. The public key is designed to be shared freely without weakening security. Exposing the private key lets anyone decrypt data meant only for the intended recipient.

Common mistakes: Line 3 encrypts using the private key, but asymmetric encryption should encrypt with the public key. Line 4 decrypts using the public key, but decryption should use the matching private key instead.

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This module's key terms are also in a printable crossword (Modules 41–50) and word search (Modules 41–74).

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Learning

Duo

Asymmetric encryption uses two different but mathematically linked keys.

TrueFalse

Matches

share_publicly(priv)

↓

The mistake: sharing the private key, which must stay secret

Applying

Meanings

Term

Asymmetric encryption

Meaning

Encryption that uses a linked pair of keys: a public key to encrypt data and a private key to decrypt it, with no shared secret key needed.

Practice

pub, priv = generate_key_pair()

Testing

Gaps

= getpublic()

Check Answer

Spots

2priv = get_private()

3ct = encrypt(msg, priv)

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Quick Questions

1. Asymmetric encryption uses two different but mathematically linked keys.

A. True ✓

B. False

A public key and a private key form a linked pair used for encryption and decryption.

2. Which key should be shared openly: the public key, or the private key?

A. Private key

B. Public key ✓

The public key is designed to be shared freely without weakening security.

3. The private key can be shared openly without any risk to security.

A. False ✓

B. True

Exposing the private key lets anyone decrypt data meant only for the intended recipient.

4. Which decrypts data encrypted with the public key: the matching private key, or the same public key?

A. The matching private key ✓

B. The same public key

Only the linked private key can correctly decrypt data encrypted with the public key.

5. Asymmetric encryption requires both parties to share the same secret key beforehand.

A. True

B. False ✓

Asymmetric encryption avoids needing a shared secret by using separate public and private keys.

Match the Pairs

ct = encrypt(msg, pub) → Encrypting data using the recipient's public key

pt = decrypt(ct, priv) → Decrypting data using the matching private key

Asymmetric encryption uses a linked pair of keys → pub, priv = generate_key_pair()

The public key can be shared openly without weakening security → share_publicly(pub)

share_publicly(priv) → The mistake: sharing the private key, which must stay secret

pt = decrypt(ct, pub) → The mistake: decrypting with the public key instead of the private key

Key Term

Asymmetric encryption

Encryption that uses a linked pair of keys: a public key to encrypt data and a private key to decrypt it, with no shared secret key needed.

Fill in the Blanks

1. public_key = get_public()

Hint: Type the name of the variable storing the public key.

2. private_key = get_private()

Hint: Type the name of the variable storing the private key.

3. ct = asym_encrypt(msg, public_key)

Hint: Type the name of the function that encrypts a message with the public key.

4. pt = asym_decrypt(ct, private_key)

Hint: Type the name of the function that decrypts ciphertext with the private key.

5. def generate_key_pair():

Hint: Type the name of the function that creates a linked public and private key.

Spot the Error

Question 1

A pub = get_public()

B priv = get_private()

C ct = encrypt(msg, priv)

Line C — Line 3 encrypts using the private key, but asymmetric encryption should encrypt with the public key.

Question 2

A pub = get_public()

B priv = get_private()

C ct = encrypt(msg, pub)

D pt = decrypt(ct, pub)

Line D — Line 4 decrypts using the public key, but decryption should use the matching private key instead.

Question 3

A pub = get_public()

B keep_secret(pub)

C priv = get_private()

Line B — Line 2 treats the public key as secret, but the public key is meant to be shared openly.

Question 4

A priv = get_private()

B share_publicly(priv)

C pub = get_public()

Line B — Line 2 shares the private key publicly, but the private key must stay secret to remain secure.

Question 5

A pub = priv

B ct = encrypt(msg, pub)

C pt = decrypt(ct, priv)

Line A — Line 1 sets the public key equal to the private key, but they must be a distinct, linked pair.

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