hcrypto.engines
Class TranspositionEngine

java.lang.Object
  |
  +--hcrypto.cipher.CipherEngine
        |
        +--hcrypto.cipher.BlockCipher
              |
              +--hcrypto.engines.TranspositionEngine

public class TranspositionEngine

extends BlockCipher

This class implements a Transposition cipher algorithm for any range of alphabets, including az, AZ, azAZ, azAZ09, printable characters, and all ASCII. A keyword is retrieved from the "TranspositionKey.html">TranspositionKey class and stored in a String instance variable. The keyword consists of a series of positive integers, i.e. "3021".

Encryption involves transposing a plaintext character from a given message with another character from the same plain text message. The basic algorithm for encrypting is:

      StringBuffer sb = new StringBuffer(blocksize);
      for (int k = 0; k < keyword.length(); k++) {
          sb.setCharAt((int)(keyword.charAt(k) - '0'), s.charAt(k));
      }
      return sb;
 

Decryption basically involves the same algorithm, only with an inverted keyword (created and retrieved from the TranspositionKey class).

      StringBuffer sb = new StringBuffer(blocksize);
      for (int k = 0; k < keyword.length(); k++) {
          sb.setCharAt((int)(invertedKeyword.charAt(k) - '0'), s.charAt(k));
      }
      return sb;

Padding and blocksize are handled in the engineEncode(String s) and engineDecode(String s) methods

See also:

TranspositionKey
Alphabet

Fields inherited from class hcrypto.cipher.BlockCipher

alphabet, blocksize, cipherAlphabet

Fields inherited from class hcrypto.cipher.CipherEngine

alphabetRangeOptions

Constructor Summary

TranspositionEngine()
Creates a TranspositionEngine and sets the alphabetRangeOptions instance variable to "111111", which translates to all six alphabet options.

Method Summary

java.lang.String	engineDecode(java.lang.String s) Returns an encoded String for the specified String.
java.lang.String	engineEncode(java.lang.String s) Returns an encoded String for the specified String.
protected void	engineInit(HistoricalKey hKey) Initializes the TranspositionEngine with the specified hKey.

Methods inherited from class hcrypto.cipher.BlockCipher

decodeShift, encodeShift, engineDecrypt, engineDecryptFile, engineDecryptFile, engineEncrypt, engineEncryptFile, engineEncryptFile

Methods inherited from class hcrypto.cipher.CipherEngine

getAlphabetRangeOptions

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TranspositionEngine

public TranspositionEngine()

Creates a TranspositionEngine and sets the alphabetRangeOptions instance variable to "111111", which translates to all six alphabet options.

Method Detail

engineInit

protected void engineInit(HistoricalKey hKey)
                   throws java.lang.Exception

Initializes the TranspositionEngine with the specified hKey.

Overrides:

engineInit in class BlockCipher

Parameters:

hKey - a TranspositionKey.

engineEncode

public java.lang.String engineEncode(java.lang.String s)
                              throws java.lang.Exception

Returns an encoded String for the specified String. Characters which are not part of the chosen alphabet set are ignored.

Overrides:

engineEncode in class BlockCipher

Parameters:

s - the String to be encrypted

engineDecode

public java.lang.String engineDecode(java.lang.String s)
                              throws java.lang.Exception

Returns an encoded String for the specified String. Characters which are not part of the chosen alphabet set are ignored.

Overrides:

engineDecode in class BlockCipher

Parameters:

s - the String to be decrypted