def METHOD_NAME(self, n):
    """n = bit length of inputs"""
    g1 = group.random(G1)
    g2, h = group.random(G2), group.random(G2)
    u_t = group.random(ZR)
    u = [group.random(ZR) for i in range(n+1)]
    U_t = g2 ** u_t
    U1 = [g1 ** u[i] for i in range(0, n)]
    U2 = [g2 ** u[i] for i in range(0, n)]
    pk = { 'U1':U1, 'U2':U2,'U_t':U_t, 'g1':g1, 'g2':g2, 'h':h,'n':n   }
    sk = { 'u':u, 'u_t':u_t, 'g1':g1, 'h':h,'n':n }
    return (pk, sk)