# TEMPORARY semicharmed - file transfer only? mask = 0xFFFFFFFFFFFFFFFF # 16 * 4 = 64 bits z0,z1 = 0,1 xorshiftseed={ 'x' : 0, 'y' : 1 } def method1(state0, state1): s1 = state0 s0 = state1 s1 ^= (s1 << 23) & mask s1 ^= (s1 >> 17) s1 ^= s0 s1 ^= (s0 >> 26) state0 = state1 state1 = s1 generated = (state0 + state1) & mask return state0, state1, generated def method2(): global xorshiftseed x,y = xorshiftseed['x'], xorshiftseed['y'] xorshiftseed['x'] = y x ^= (x << 23) & mask # a xorshiftseed['y'] = x ^ (x >> 17) ^ y ^ (y >> 26) # b,c return (xorshiftseed['y'] + y) & mask # return value can only be exactly represented or have a 1 cut off (F+F = 1E) for i in range(10): z0, z1, gen = method1(z0,z1) print('{} \t {} \t {}'.format(z0,z1,gen)) tmp = method2() # loads xorshiftseed #print('2', xorshiftseed['x'], xorshiftseed['y'], tmp) last_x = xorshiftseed['x'] last_y = xorshiftseed['y'] def reverse17(val): return val ^ (val >> 17) ^ (val >> 34) ^ (val >> 51) def reverse23(val): return (val ^ (val << 23) ^ (val << 46)) & 0xFFFFFFFFFFFFFFF def xs128p_backward(state0, state1): prev_state1 = state0 prev_state0 = state1 ^ (state0 >> 26) prev_state0 = prev_state0 ^ state0 prev_state0 = reverse17(prev_state0) prev_state0 = reverse23(prev_state0) generated = (prev_state0 + prev_state1) & 0xFFFFFFFFFFFFFFFF return prev_state0, prev_state1, generated print("_____ Go back one step _____") print(xs128p_backward(last_x, last_y)) """ print("\nUsing x ({}) to recover y...".format(orig_x)) print('{0:b}:{1}'.format(orig_x, orig_x)) print(' '*17 + '{0:b}'.format(orig_x >> 17)) top34 = (orig_x >> 17) ^ orig_x print('{0:b}:{1}'.format(top34, top34)) print(' '*51 + '{0:b}'.format(top34 >> 17)) top51 = orig_x ^ (top34 >> 17) print('{0:b}:{1}'.format(top51, top51)) print(' '*64 + '{0:b}'.format(top51 >> 17)) # 13 signif original = orig_x ^ (top51 >> 17) print('{0:b}:{1}'.format(original, original)) bot46 = original ^ (original << 23) bot46 = (original ^ (original << 23)) & 0x3fffffffffff original = (original ^ (bot46 << 23)) & 0xFFFFFFFFFFFFFFFF print("{0:b}:{1}".format(original, original)) print("="*30) print('1>{0:b}:{1}'.format(tmp, tmp)) tmp = (tmp >> 23) ^ tmp print('2>{0:b}:{1}'.format(tmp, tmp)) prev_y = (tmp >> 46) ^ tmp # recovering y from the previous step... print('3: {} recovered from previous step'.format(prev_y)) # using y from this step.... print("\nUsing y ({}) to recover x...".format(xorshiftseed['y'])) tmp = ((xorshiftseed['y'] << 26) & mask) ^ xorshiftseed['y'] print('1>{0:b}:{1}'.format(tmp, tmp)) tmp = tmp ^ ((tmp << 26) & mask) print('2>{0:b}:{1}'.format(tmp, tmp)) prev_x = tmp ^ ((tmp << 52) & mask) # recovering x from previous step print('3: {} recovered from previous step'.format(prev_x)) """ """ // c++ xorshift128plus generator (1D distributed) #include /* The state must be seeded so that it is not everywhere zero. */ uint64_t s[2]; uint64_t xorshift128plus(void) { uint64_t x = s[0]; uint64_t const y = s[1]; s[0] = y; x ^= x << 23; // a s[1] = x ^ y ^ (x >> 17) ^ (y >> 26); # b, c return s[1] + y; } """

TEMP: semicharmed PRNG