Symmetric encryption
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Does symmetric encryption use the same key to lock and unlock a message?
2. Should the shared key be kept secret between both people?
3. Is it safe to share the key openly with everyone?
4. Can a different key unlock a message that was locked with the shared key?
5. Which is usually faster: symmetric encryption, or using two separate keys?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1Lock a message | AThis breaks security - anyone could unlock the message | |
| 2Unlock a message | BLock and unlock with the same key | |
| 3Symmetric encryption uses just one key for both jobs | CThis won't work - only the same key can unlock it | |
| 4The shared key must be kept secret | DUses that exact same shared key | |
| 5Posting the shared key somewhere public | EUses the shared key | |
| 6Using a different key to unlock the message | FNever share it with anyone who doesn't need it |
C
Definitions
Symmetric encryption
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
Symmetric encryption uses the ____
key to lock and unlock.
2.
The shared key must stay ______
between both people.
3.
You must _____
the key safely with the other person.
4.
Using a _________
key to unlock will not work.
5.
Symmetric encryption is usually ______
than using two keys.
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
Same key locks and unlocks
B
Different key locks and unlocks
C
Key must stay secret
Question 2
A
Key must stay secret
B
Key is safe to share with everyone
C
Same key locks and unlocks
Question 3
A
Same key locks and unlocks
B
Key must be shared safely
C
Key should be shared publicly
Question 4
A
Different key unlocks it fine
B
Same key unlocks it correctly
C
Key must stay secret
Question 5
A
Same key locks and unlocks
B
Key must stay secret
C
Key must be shared safely
D
Sharing the key openly is fine
Answer Key
Symmetric encryption
Section A: Quick Questions
Q1
B — Yes
Q2
A — Yes
Q3
B — No
Q4
A — No
Q5
A — Symmetric encryption
Section B: Match the Pairs
Q1
Lock a message → Uses the shared key
Q2
Unlock a message → Uses that exact same shared key
Q3
Symmetric encryption uses just one key for both jobs → Lock and unlock with the same key
Q4
The shared key must be kept secret → Never share it with anyone who doesn't need it
Q5
Posting the shared key somewhere public → This breaks security - anyone could unlock the message
Q6
Using a different key to unlock the message → This won't work - only the same key can unlock it
Section C: Definitions
Q1
Symmetric encryption — Using the exact same secret key to both lock and unlock a message.Section D: Fill in the Blanks
Q1
Symmetric encryption uses the same
key to lock and unlock.Q2
The shared key must stay secret
between both people.Q3
You must share
the key safely with the other person.Q4
Using a different
key to unlock will not work.Q5
Symmetric encryption is usually faster
than using two keys.Section E: Spot the Error
Q1
B — Line 2 says a different key locks and unlocks, but symmetric encryption uses the exact same key for both.
Q2
B — Line 2 says the key is safe to share with everyone, but the shared key must stay secret between the two people.
Q3
C — Line 3 says the key should be shared publicly, but it must only be shared safely with the other trusted person.
Q4
A — Line 1 says a different key unlocks it fine, but only the exact same key can correctly unlock the message.
Q5
D — Line 4 says sharing the key openly is fine, but the key must be shared safely and kept secret from others.