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Intro to CS 9-10 / Week 12 / Tuesday
2/6
Week 12 · Safe, Fair and Ready: Beacon Launch Review

Tuesday

Locks and keys
// Privacy, security, fairness and a launch day demo
⏱ about 20 min

Tuesday: Locks and Keys

Comet proudly shows the new mission control sign-in. "The password is basil. Everyone knows I love basil, so nobody forgets."

Wren tilts his head. "What do you notice? If everyone knows you love basil, everyone can guess it."

Comet deflates a little. "Then I will make it super long. Forty letters, all random."

"And the plant team will write it on a sticky note by the door," Wren says.

Nova hovers between them. "Safe and easy to use pull in different directions," she says. "Find a balance."

Comet sits down with a fresh page. "Two steps, maybe. Something you know and something you carry."

Authentication

Authentication measures protect devices and information from unauthorized access. Strong passwords and multifactor authentication are examples.

A strong password is easy for its user to remember. It is hard for someone else to guess, even someone who knows that user.

Multifactor authentication asks for at least two kinds of evidence. The kinds are something you know, something you have and something you are.

Never share a real password, in this course or anywhere else. Every password here is invented.

KNOW, HAVE OR ARE?
  • Read the question.
  • Tap your answer.
A made-up password that Wren memorized is...
A badge card that Comet carries is...
A fingerprint is...
Why is basil a weak password for Comet?

Encryption

Encryption is encoding data to prevent unauthorized access. Decryption is decoding it back.

Symmetric key encryption uses one key for both encrypting and decrypting.

Public key encryption pairs a public key for encrypting with a private key for decrypting.

Here is an analogy, not how the math works: a locked mailbox with a slot. Anyone can drop a letter in, but only the private key opens the box.

WHICH KIND OF ENCRYPTION?
  • Read the question.
  • Tap your answer.
Beacon and mission control share one secret key, and it both locks and unlocks messages. Which kind?
Anyone may lock a message for mission control with its public key, but only its private key unlocks it. Which kind?

Safe versus easy

Choosing security measures means trading off usability and security.

The needs of the users and how sensitive the data are decide how much security is right.

A good choice also weighs efficiency, feasibility and ethical impacts.

StatementTrue or false?
Multifactor authentication uses at least two kinds of evidence.?
A forty-letter random password is always the best choice for every user.?
Decryption decodes encrypted data.?
More sensitive data usually call for more security.?
WHY THIS EXERCISEGood security fits the users and the data, not just the strongest lock.
A TWO-STEP SIGN-IN, IN ORDER
  • ?A crew member types their name.
  • ?They enter something they know.
  • ?They tap the badge card they carry.
  • ?Beacon checks both and opens mission control.
WHY THIS EXERCISETwo kinds of evidence make a sign-in much harder to fake.
Encoding data to stop unauthorized access is ____.
Encryption that uses one key both ways is ____ key encryption.
Protecting devices by checking who someone is is called ____.
Which kind of evidence is a badge card: know, have or are? Type one word.
WHY THIS EXERCISEKnowing the three kinds helps you design multifactor authentication.
Try it
With a grown-up, list three locks or codes your family uses, such as on a door, a bike or a locker.
For each, is it something you know, something you have or something you are?
On paper, sketch the screens of Beacon's two-step sign-in. Use only invented names.

Great security thinking. Tomorrow's Beacon Lab is the launch review itself.

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