Encryption is used to secure information transmitted online. It works by encoding information using a key so that only someone with the key can decode it. There are two main types of encryption: symmetric-key encryption which uses the same key to encrypt and decrypt, and asymmetric or public-key encryption which uses two different but linked keys, a private key and a public key. Public-key encryption involves encrypting a symmetric key with the recipient's public key and then encrypting the message with the symmetric key. A popular implementation of public-key encryption is Secure Sockets Layer (SSL) which transmits sensitive information securely over the internet.

1. The Internet became indispensable to our
life. We do shopping on a net with a credit
card. We do the transfer to the bank account
on a net. Those information does not want to
be known. Therefore we save it to mediums
such as the flash memory. the most popular
forms of security all rely on encryption, the
process of encoding information in such a
way that only the person with the key can
decode it.

2. Computer encryption is based on the
science of cryptography, which has been used
as long as humans have wanted to keep
information secret. For example the Greek
made a code with a specific cord including the
substitution of the letter and number or the
transposition. Most forms of cryptography in
use these days rely on computers, simply
because a human-based code is too easy for a
computer to crack.

3. A key, on the other hand, helps a person or
computer figure out the one possibility on a
given occasion. Computers using symmetric-
key encryption to send information between
each other must have the same key.
Symmetric-key encryption is essentially the
same as a secret code that each of the two
computers must know in order to decode the
information. The code provides the key to
decoding the message.

4. known as asymmetric-key encryption,
public-key encryption uses two different keys
at once -- a combination of a private key and a
public key. The sending computer encrypts the
document with a symmetric key, then encrypts
the symmetric key with the public key of the
receiving computer. The receiving computer
uses its private key to decode the symmetric
key. It then uses the symmetric key to decode
the document.

5. The key to public key encryption is based
on hash value. This is value calculated from a
base input number using algorithm performing
a hash. The hash value is a summary of the first
value basically. The important thing about the
hash value is that it is almost impossible to
draw an original input number without knowing
the data which are used to make hash value.

6. A popular implementation of public-key
encryption is the Secure Sockets Layer (SSL).
Originally developed by Netscape, SSL is an
Internet security protocol used by Internet
browsers and Web servers to transmit sensitive
information. SSL has become part of an overall
security protocol known as Transport Layer
Security (TLS).