I can't imagine any legitimate use case for crappy cryptography, and any crypto with a backdoor is crappy. If the door is there, anyone with the key can open it. How can you be sure who will get the key, or what their motives will be?
Good, modern cryptography offers a level of security unparalleled in the physical world, and at a processing cost which any computer can handle. Why would you intentionally choose something inferior?
Good, modern cryptography offers a level of security unparalleled in the physical world, and at a processing cost which any computer can handle. Why would you intentionally choose something inferior?