crypto.graphics

Message Authentication Code (MAC) Security Game

{Sign, Verify} is the candidate MAC scheme.



k = rand(Keys)

i++
mi mi ∈ Inputs
ti = Sign(k, mi) ti
(m*, t*) ∈ Outputs: (∀ i) m* ≠ mi
(m*, t*)

Advantage

  • Advantage(Adversary) = Pr[Verify(k, m*, t*) accepts the tag as valid]


Correctness

  • (∀ m) Pr[k ← genKeys(), Verify(k, m, Sign(k, m)) == accept ] == 1