Encryption encodes information so that only those with the key can access it. There are two main types: symmetric key encryption which uses the same key to encrypt and decrypt but must be installed on both computers beforehand, and public key encryption which addresses issues with symmetric key and uses different keys but allows anyone to encrypt messages. One popular public key encryption program is PGP.

1. How Encryption Works
OUTLINE
When we use the Internet, we're not
always just clicking around and
passively taking in information. For
example, it is reading news articles or
blog posts. A great deal of our time
online involves sending others our own
information.

2. Information security is provided on computers
and over the Internet by a variety of
methods. The most popular forms of security
all rely on encryption, the process of
encoding information in such a way that only
the person (or computer) with the key can
decode it.
This article is written about learning about
public-key and symmetric-key systems, as well
as hash algorithms.

3. ・Security Encryption Systems
Computer encryption is based on the science
of cryptography, which has been used as long
as humans have wanted to keep information
secret. The Greek historian Plutarch wrote,
for example, about Spartan generals who sent
and received sensitive messages using a
scytale, a thin cylinder made out of wood.

4. ・Symmetric Key
You need two Spartan generals sending
messages to each other, computers using
symmetric-key encryption to send information
between each other must have the same key.
Symmetric-key requires that you know which
computers will be talking to each other so
you can install the key on each one.
The code provides the key to decoding the
message.

5. ・Public Key Encryption
An attacker can easily pluck the
necessary data from the stream. In
November 1976, a paper published in the
journal IEEE Transactions on Information
Theory, titled "New Directions in
Cryptography," addressed this problem
and offered up a solution

6. In November 1976, a paper published in
the journal IEEE Transactions on
Information Theory, titled "New
Directions in Cryptography," addressed
this problem and offered up a solution.
One very popular public-key encryption
program is Pretty Good Privacy (PGP),
which allows you to encrypt almost
anything.