COMPUTER NETWORK SECURITY PART 2
Back again in the network security article we just
discussed for part 2
II.
BASIC SECURITY INFORMATION SYSTEM
Data security can be
done in two ways, namely:
1.
Steganography
In Wikipedia mentioned
that steganography comes from the Greek word steganos which means is disguise
or penyembuyian and graphein which means is writing. So steganography can be
interpreted as the art of disguising / hiding written messages into other
messages. The concealment or disguise of this message is made in such a way
that the other party does not know that there are 'other messages' in the
message being sent. Only the legitimate recipient can know the 'other' message.
In contrast to
cryptography , where the character of the message is changed / randomized into
another meaningless form, the steganography of its message itself is retained
only in its delivery obscured in various ways. Messages delivered
cryptographically become suspicious because of its 'meaninglessness'. While the
message in steganography, looks like a regular message so it is less likely to
be suspected.
The techniques of
concealment / blurring of this message vary, from ancient to ancient to
advanced in this computer age. For example, write a message on the wood panel
which then hidden by coating the wax as a cover which is known as wax tablets.
Historically, Demeratus (the Greeks) performed in 400 BC. In World War II there
was recorded a text messaging technique that was reduced to a point (microdots)
placed under postage and message hiding using invisible ink. Message masking
can also use images, paintings, articles, shopping lists, magazines or
electronic / digital media commonly referred to as digital watermarking such as
MP3 files, videoclips, digital images, document files and others that function
as covertext or message closers .
That there is no perfect
security applies also in steganography, because the method of detecting
messages in steganography was much developed which is called steganalisis.
Steganalysis is a technique of analysis to reveal the existence of
steganography.
2.
Cryptography
Cryptography
(cryptography) is a science and art to keep message to be safe. (Cryptography
is the art and science of keeping messages secure. [27]) "Crypto"
means "secret" and "graphy" means "writing"
(writing) [2]. The perpetrators or practitioners of cryptography called
cryptographers. A cryptographic algorithm (cryptographic algorithm), called a
cipher, is a mathematical equation used for encryption and decryption process.
Usually both mathematical equations (for encryption and decryption) has a
fairly close mathematical relationship. The process is done to secure a message
(which called plaintext) into a hidden message (called ciphertext) is
encryption (encryption). Ciphertext is a message already can not be read
easily. According to ISO 7498-2, the more appropriate terminology to use is
"encipher". The reverse process, to convert ciphertext to plaintext, called
decryption. According to ISO 7498-2, that terminology more appropriate for this
process is "decipher". Cryptanalysis is the art and science to solve
ciphertext without the help of a key.
Cryptanalyst is the
actor or practitioner run cryptanalysis.Elements of EncryptionEncryption is
used to encode data or information so it can not be read by unauthorized
people. With Your encryption data is encrypted by using a key (key). To open
(decrypt) the data also used a key that can be the same as the key for encrypt
(for private key cryptography) or with different keys (for the case of public
key cryptography). Mathematically, the process or function of encryption (E)
can be written as: E (M) = C where: M is plaintext (message) and C is
ciphertext. Decryption process or function (D) can be written as: D (C) = M There
are several elements of encryption that will be spelled out in a few paragraphs
below. Algorithm of Encryption and Decryption. The algorithm of the encryption
is functions used to perform encryption functions and decryption. The algorithm
used determines the power of encryption, and this is usually proved by a
mathematical basis.
Lock used and lock
length. The power of encoding depending on the key used. Some algorithms encryption
has a weakness in the key used. For that weak key should not be used. Other
than that, the length of the key, which is usually in bit size, as well determine
the strength of the encryption. Longer key usually safer than a short key. So
encryption with using a 128-bit key is more difficult to break with the same encryption
algorithm but with a 56-bit key. Increasingly the length of a key, the greater
the keyspace to be lived to search for keys by brute force attack or trial and
error because the keyspace to be seen is the power of number 2. So the 128-bit
key has keyspace 2128, whereas 56-bit keys have keyspace 256. This means longer
keys can only be discovered. Plaintext. Plaintext is a message or information
that is sent. E (M) = C D (C) = MThere are several elements of encryption that
will be spelled out in a few paragraphs below. Algorithm of Encryption and
Decryption. The algorithm of the encryption is functions used to perform
encryption functions and decryption. The algorithm used determines the power of
encryption, and this is usually proved by a mathematical basis. Lock used and
lock length. The power of encoding depending on the key used. Some algorithms encryption
has a weakness in the key used. For that weak key should not be used. Other
than that, the length of the key, which is usually in bit size, as well determine
the strength of the encryption. Longer key usually safer than a short key. So
encryption with using a 128-bit key is more difficult to break with the same
encryption algorithm but with a 56-bit key. Increasingly the length of a key,
the greater the keyspace to be lived to search for keys by brute force attack
or trial and error because the keyspace to be seen is the power of number 2. So
the 128-bit key has keyspace 2128, whereas 56-bit keys have keyspace 256. This
means longer keys can only be discovered.
Plaintext is a message
or information sent. Ciphertext is information that has been encrypted. Enigma Rotor Machine Enigma rotor machine is an encryption tool used in the second
world war. He is made up of several rotor and crossed crosses lead to
substitution the ever-changing alphabet.
3. Key
Usage
One way to increase a
security level encryption and decryption algorithm is to use a key that is
usually called K. This K key can has a range (range) is quite wide. Range of the
possible number (price) of the key K is called the keyspace. Key K is used in
the process of encryption and decryption so the mathematical equation becomes: The
security system used later is not dependent to the knowledge of the algorithm
used, but rather depending on the key used. That is, the algorithm can publicly
known or published. Effort to break the security of the system into an attempt
to solve or search for the key used.
The search for a key
depends heavily on the keyspace of the key K. If the keyspace is small enough,
then brute force or trying all the keys can be done. But if keyspace of the key
used is quite large, then effort to try all key combinations to be unrealistic.
Keyspace from DES, for example, has 56-bit. To try all combinations are
required combination. (Story about the weakness of DES will be phrased
elsewhere.)
4. Application
from Encryption
An example of using
encryption is the Pretty Good Privacy program (PGP) [11], and secure shell
(SSH). The PGP program is used for encrypt and add digital siganture in e-mail sent.
The SSH program is used to encrypt telnet sesion to a host. This will be
further discussed elsewhere. The difference in principle and the use of
public-key cryptography and symmetric cryptography requires a separate
discussion. On symmetric cryptography, the same key used for perform encryption
and decryption. On a public-key system cryptography, encryption and decryption
using that key different. Since the development of public-key cryptography, it
always arises which question is better. Cryptographers saying that both can not
be compared because they solve the problem in different domains. Symmetric
cryptography is the best thing to do encrypt data. Its speed and security will
be choosenciphertext attack is the advantage. Meanwhile public-key cryptography
can do other things better than symmetric cryptography, for example in terms of
key management.