Signature Verification Worksheet

Purpose: Verify that the message and signature on your physical clue are authentic using simplified cryptographic signature verification.

How Digital Signatures Work

In cryptographic systems like Bitcoin:

Signing: The sender uses their private key to create a signature for a message
Verification: Anyone can use the sender's public key to verify the signature
Security: The signature proves the message came from the private key holder without revealing the private key

This worksheet simulates a simplified version of RSA signature verification.

Step 1: Record Your Clue Data

Copy the information from your physical clue card into the boxes below:

Message (M):

Public Key (e, n): e = , n =

Signature (S):

💡 Example values you might see: Message = "KEY42", e = 7, n = 143, Signature = 42

Step 2: Hash the Message

Calculate H = hash(Message)

We'll use a simplified hash function: sum the ASCII values of each character in the message, then take modulo n.

H = (sum of ASCII values) mod n

Message: ____________________

Break down each character:

Character	ASCII Value





Sum =

Calculate Hash:

H = _________ mod _________ =

💡 ASCII Quick Reference: A=65, B=66, C=67... Z=90, 0=48, 1=49, 2=50... 9=57
Use an ASCII table or your phone to look up values.

Step 3: Verify the Signature

Calculate V = S^e mod n

Apply the public key operation to the signature to get the verification value.

V = S^e mod n

Given values:

Signature (S) =

Public exponent (e) =

Modulus (n) =

Step-by-step calculation:

1. Calculate S^e = =

2. Calculate (S^e) mod n:

mod =

Verification Value (V) =

💡 Calculation Tips:

Use a calculator for exponentiation (x^y button)
For modulo: divide the large number by n, then multiply the remainder by 1
Example: 125 mod 11 = 125 ÷ 11 = 11 remainder 4, so answer is 4

Step 4: Compare and Conclude

Does H = V?

Compare your hash value (H) from Step 2 with your verification value (V) from Step 3.

H (Hash of Message) =

V (Verification Value) =

Are they equal?

☐ YES - The signature is VALID
☐ NO - The signature is INVALID/FORGED

Verification Result

The signature on our clue is:

Explanation:

Security Reflection Questions

Answer the following questions to demonstrate your understanding:

Question 1: Interception

What would happen if someone intercepted your encrypted message during the treasure hunt?

Question 2: Public Key Security

How does the public key help verify the signature without revealing the private key?

Question 3: Real-World Applications

Name at least two real-world applications that use digital signature verification like this:

Team Signatures

All team members who contributed to this verification:

Name	Signature	Role in Activity

Verification Worksheet | Submit with puzzle solution | Page 1 of 1