Cryptography uses advanced mathematics to make it possible to hide a message. Cryptography is sometimes called dual use technology because aside from its good applications, it can also be applied for evil purposes. Some countries choose to forbid the use of cryptography... as if terrorists would not use these principles illegally!
Compare a standard text to another, seemingly harmess text and you will not notice any difference.
Now, view the documents with
view source code, and compare that.
You may notice that the spacing is different -- your browser hid this from you.
That looks innocent but in the latter document, this spacing contains a hidden message!
Techical specification: Two spaces encode a
1 bit, one space encodes a
0 bit, and it is serialised with the most significant bit first.
Compare this hidden encryption to an encrypted message in OpenPGP format; this is obviously not plain text. To decrypt the message from this one, you also need the receiving-side secret key and the corresponding public key and any PGP implementation (beware, this is complicated software).
A smart person is able to hide whatever he wants, this simple demo is really not fancy at all. A government can impossibly ban all such things from existence -- not from truely persistent underground movements. In conclusion, there is no gain in outlawing cryptography. Sad as it may be, negative forces will always find ways to exploit means intended for good use. It's a fact of live, and we have to live with it.