> The superficial solution to this is not to outlaw cryptography completely, but to require those who make cryptography available to keep master keys and/or logs.

The infrastructure keeping those keys then becomes an irresistible target to compromise. The government has already lost critical data such as the application data for most/all Classified personnel in the military and contractors. If that kind of data cannot be kept safe then you can be sure that a legally centralized infrastructure to keep keys will be attacked, and likely compromised at some point.