How Does Encryption Work? Explained

[physics kiddy]

I read about methods of encryption and I guess that they work only when you are online. But, I was astonished to see Compress or Encrypt attributes in Properties --> General --> Advanced. Please explain what's the need of encrypting any folder and what happens when a folder is encrypted. Frankly saying, I could see nothing except the name of the folder written in green text when I try to encrypt any folder.

 

[DaleSwanson]

Encryption is a huge subject. In addition, you seem to be asking why bother with encryption rather than how it works. As for why, the reason is simply to prevent others from viewing your data. A common example would be if someone steals your laptop. If your files are unencrypted then the thief will have access to a variety of personal data, some of which could be very valuable.

You mention online, which implies totally different types of encryption. In the case of online communications, the encryption is used to protect communications from eavesdropping. In general you should assume that your internet connection can be monitored by anyone with sufficient motivation to do so. By encrypting your data you ensure that even if they can see the communications that can't actually read the contents.

An interesting question is how can you communicate securely with someone you've never met, or exchanged a password with, while a hostile third party watches all your communications. At first this may seem impossible, but it is not. Every time you connect to a secure website (one that starts with https) you and that site are exchanging keys in a way that a eavesdropper can't see. This is done by asymmetric encryption (aka public key encryption), and is generally slower and less secure than symmetric (aka normal encryption). Therefore, the asymmetric encryption is used only to exchange a random key so that symmetric encryption can then be used. This is called key exchange, and is quite interesting (at least to me):
http://en.wikipedia.org/wiki/Key_exchange"

If you are interested in learning more about how encryption works, I highly recommend this guide:
http://www.moserware.com/2009/09/stick-figure-guide-to-advanced.html"

It is split into 4 sections, starting quite basic, and finally going into quite a bit of detail.

If you are interested in encrypting your personal files a program called Truecrypt is free/open source, and quite good. You can encrypt your entire hard drive so that you need to enter a password to access it. If you use a strong passphrase the encryption will hold up against the strongest known attacks (that is, even if a government wants your files they will be unlikely to crack it, of course there are http://xkcd.com/538/" ).
http://www.truecrypt.org/"