Method of Encryption

Posted: October 17, 2012 in Sistem Keamanan Komputer
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1.  Here are the examples of using Caesar cipher methods to find out plaintext in a sentences which has been encrypsied.

      Examples ofcipherthat will besolved :


  • On the cipher above, there are 6 spaces, it means that we have gotten six plaintext (a space also counted as one as one character)
  • Look for the suspicious and short words first, consist of one two or three words or the repetition words
  •  The example of cipher above, there are two words which can be two indicator, namely LV and RI

  • In English the words are composed of two characters namely : is, of, on, in, etc.
  • If using the word “on” to encryption, then we do not have the correct algorithm and is not suitable for cipher WKLV
  • If using the word “is” to encrypt the LV, then get the algorithm P (plaintext) = C (Caesar)-3.
  • Use a table that contains a combination of letters to the algorithm P = C-3 to facilitate the conversion of cipher into plaintext, example table is:

  • By using the above tableobtainedplaintext=THISISSECONDTASKOF COMPUTER  SECURITYSYSTEM

1.       2.   Encryption algorithm using a key (k)

     This is an 5 example of encryption that uses multiple keys (K) for the same plain text:

      Plaintext = say no to drugs

      Key (K) = computer

     Plaintext = say no to drugs

      Key (K) = Aquarium

      Plaintext = say no to drugs

      Key (K) = chair

      Plaintext = say no to drugs

      Key (K) = scissor

      Plaintext = say no to drugs

      Key (K) = complete


     weakness of the encryption using a key:

  • The key must be sent via a secure channel. Both entities must maintain the confidentiality of communication is the key.
  • Keys must be frequently changed, perhaps at each communication session.
  • There are some of the same font as plaintext
  • If the key (K) is known by others it will be very easy to break the encryption code.
  • at the end of the alphabet such as v, w, x, y, z plaintext and the encryption is often not changed


      excellence :

  • plaintext is not known if the encryption key is not known in advance
  • The algorithm is designed so that the process of encryption / decryption takes a short time.
  • key size is usually much shorter
  • The algorithm can generate a stronger cipher.
  • Authentication messages immediately known from the received ciphertext, because the key only known by the sender and the recipient only.
  • if the key word is unknown it is difficult to know the plain text / encryption can be changed easily by changing the key word

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