From time to time the bells are ringing for laws to prohibit “encryption”.

While most of the time it is desired to prevent criminals from exchanging information without the authorities being able to read the content, encryption in general is neither good nor evil by nature. It is also nothing a computer does magically and you could disable or forbid.

Encryption is based on pure mathematics.

Disallowing or preventing encryption would require disabling/disallowing mathematic procedures which would generally question central processing units.

Would criminals abide the speed control after a bank robbery? Would terrorists stop using encryption because it is forbidden?

On the other side there are many legitimate uses for encryption. For example, when using an IP video camera at home, which you can access via your smartphone, you do not want anyone to be able to see that you are at home or not. If this data is unencrypted, it would be easy for thieves to see when you leave your house to break into it.

Furthermore, criminals/terrorists use even more steganography than cryptography. While cryptography ensures the contents of information is protected. Steganography is used to hide the existence of information.

For example, you could send an image to another person and every x pixel is not only just the color and position information, it is also a part of a message. The recipient just needs to look at the respective pixels in the image to extract the hidden message. To anyone else it just looks like a regular picture. Of course both techniques can be combined so that in case the hidden information was detected, the content would still be protected.

It would also be possible to hide a steganography message in a video camera stream. But would you recommend sharing a private video camera with anyone?

Yes you can pass laws to prohibit encryption but they’ll never beat mathematic laws…

2 plus 2 will always be 4.