Hardware Security

1. As her Christmas gift, Joyce received a toy doll with a small computer chip embedded. When she presses the tummy of the doll, it says "Hello, Joyce!"; when she presses again, it says "Merry Christmas!"; on the next press, it says "I love you!"; and whenever Joyce presses twice quickly, it says "Good-bye!". The following statements about the doll are correct:

• The chip can recongize two different inputs
• The chip contains memory elements 

However, the chip is NOT a synchronous system because the system responses at the press any time
  and
The chip is NOT a combinational system on the same press, it may have different outputs.

2. Following gate(s) are universal:

• NAND
• NOR
• {AND, NOT}
• {OR, NOT}

3. For the 3-input gate f(x,y,z) = x’yz+xy’+y’z, what is the value of f(x,0,1)?
 
Solution
f(x, y, z)
=x'.0.1+x.1+1.1
=0 + x + 1
=1