Digital Signatures and message Authentication Code(Mac)overview Suppose alice and Bob share a secret key k which determines hash function hk Alice sends(x, y) to Bob where y=hk(x) Bob receives(x, y) and verifies with y h, (x). If condition holds, neither x nor y was modified in transit4 Digital Signatures and Message Authentication Code (MAC) overview • Suppose Alice and Bob share a secret key k which determines hash function hk • Alice sends (x, y) to Bob where y = hk (x) • Bob receives (x,y) and verifies with y = hk (x). If condition holds, neither x nor y was modified in transit