ECDSA
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. ECDSA uses the private key to create a signature and the public key to verify it.
2. Which key should be used to create a signature: the private key, or the public key?
3. It's safe to share your private key so others can verify your signature.
4. Which is used to check a signature's authenticity: the sender's public key, or their private key?
5. A valid ECDSA signature confirms that a message hasn't been altered since it was signed.
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1signature = sign(message, priv) | AThe mistake: exposing the private key, which must stay secret | |
| 2valid = verify(message, signature, pub) | Bif valid == True: | |
| 3ECDSA uses a private key to sign and a public key to verify | Cpriv, pub = gen_keys() | |
| 4A valid signature proves the message came from the claimed signer | DThe mistake: swapping the order of the message and signature arguments | |
| 5share_publicly(priv) | ECreating a signature for a message using the private key | |
| 6valid = verify(sig, msg, pub) | FChecking a signature's authenticity using the public key |
C
Definitions
ECDSA
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
_________ = sign(message, priv)
2.
signature = ____(message, priv)
3.
valid = ______(message, signature, pub)
4.
priv, pub = ________()
5.
if valid __ True:
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
sig = verify(msg, priv)
B
valid = verify(msg, sig, pub)
C
print(valid)
Question 2
A
sig = sign(pub, priv)
B
valid = verify(msg, sig, pub)
C
print(valid)
Question 3
A
sig = sign(msg, priv)
B
priv = pub
C
valid = verify(msg, sig, pub)
Question 4
A
sig = sign(msg, priv)
B
valid = sign(msg, sig)
C
print(valid)
Question 5
A
sig = sign(msg, priv)
B
valid = verify(msg, sig, pub)
C
pub = None
Answer Key
ECDSA
Section A: Quick Questions
Q1
A — True
Q2
A — Private key
Q3
B — False
Q4
A — The sender's public key
Q5
B — True
Section B: Match the Pairs
Q1
signature = sign(message, priv) → Creating a signature for a message using the private key
Q2
valid = verify(message, signature, pub) → Checking a signature's authenticity using the public key
Q3
ECDSA uses a private key to sign and a public key to verify → priv, pub = gen_keys()
Q4
A valid signature proves the message came from the claimed signer → if valid == True:
Q5
share_publicly(priv) → The mistake: exposing the private key, which must stay secret
Q6
valid = verify(sig, msg, pub) → The mistake: swapping the order of the message and signature arguments
Section C: Definitions
Q1
ECDSA — A digital signature algorithm that uses a private key to sign a message and the matching public key to verify it.Section D: Fill in the Blanks
Q1
signature = sign(message, priv)Q2
signature = sign(message, priv)Q3
valid = verify(message, signature, pub)Q4
priv, pub = gen_keys()Q5
if valid == True:Section E: Spot the Error
Q1
A — Line 1 calls verify() to create the signature, but sign() should be used with the private key to create it.
Q2
A — Line 1 passes the public key pub as the message, but sign() should take the actual message being signed.
Q3
B — Line 2 overwrites priv with pub, but the private key must stay distinct and secret for signing.
Q4
B — Line 2 calls sign() again instead of verify(), so the signature is never actually checked.
Q5
C — Line 3 discards the public key after verifying, but it may be needed again to verify future signatures.