Diffie-Hellman
Level 8
10 Points
Instructions
Diffie-Hellman key exchange.
Alice and Bob use Diffie-Hellman key exchange to share secrets. They start with prime numbers, pick private keys, generate and share public keys, and then generate a shared secret key.
Step 0
The test program supplies prime numbers p and g.
Step 1
Alice picks a private key, a, greater than 1 and less than p. Bob does the same to pick a private key b.
Step 2
Alice calculates a public key A.
A = g**a mod pUsing the same p and g, Bob similarly calculates a public key B from his private key b.
Step 3
Alice and Bob exchange public keys. Alice calculates secret key s.
s = B**a mod pBob calculates
s = A**b mod pThe calculations produce the same result! Alice and Bob now share secret s.
Diffie-Hellman
Level 8
10 Points
Instructions
Diffie-Hellman key exchange.
Alice and Bob use Diffie-Hellman key exchange to share secrets. They start with prime numbers, pick private keys, generate and share public keys, and then generate a shared secret key.
Step 0
The test program supplies prime numbers p and g.
Step 1
Alice picks a private key, a, greater than 1 and less than p. Bob does the same to pick a private key b.
Step 2
Alice calculates a public key A.
A = g**a mod pUsing the same p and g, Bob similarly calculates a public key B from his private key b.
Step 3
Alice and Bob exchange public keys. Alice calculates secret key s.
s = B**a mod pBob calculates
s = A**b mod pThe calculations produce the same result! Alice and Bob now share secret s.