Easy XOR encryption. For find the key just input empty message since key^0=key:
Metal Gear Felix
Another easy task. A video on youtube is provided with an arithmometer and some calculcation done on it. The machine was a russian Felix Arithmometer. After googled it on its operation we just put all the caluculations together:
php -r 'echo (524813609 * 7) + (5248136090 * 3) + (52481360900 * 3) + (524813609000 * 1) - (5248136090) .
And get the result: 696427659143