hcrypto.engines
Class AffineKey

java.lang.Object
  hcrypto.cipher.HistoricalKey
      hcrypto.engines.AffineKey

public class AffineKey
extends HistoricalKey

Represents a key for an Affine cipher. The key is entirely represented by two integers, a and b, which serve as variables in the Affine functions: encrypt(x) = ax + b mod N and decrypt(y) = inverse_of(a) * (y - b) mod N where N = size of the alphabet.

For a good overview of Affine cipher see the discussion on Wikipedia.

Example key and argument: 3,3/az+AZ yourTEXThere

NOTE: The Affine algorithm does not accept digits (0..9) as part of the alphabet.

This implementation of the Affine cipher is restricted to condition that the plaintext alphabet and ciphertext alphabet must have the same size.

See also:

AffineEngine
Alphabet

Field Summary

static java.lang.String	DEFAULT_KEY_DESCRIPTOR_PROMPT_STRING A description for an Affine Key.
static java.lang.String	DEFAULT_KEYWORD_STRING Default key values.

Constructor Summary

AffineKey()

Method Summary

java.lang.String	getAlgorithm() Returns the algorithm name "Affine".
int	getKeyA() Returns the keyA value for the Affine function.
int	getKeyB() Returns the keyB value for the Affine function.
void	init(java.lang.String keyspec) Creates an AffineKey with the specified keyspec.
void	init(java.lang.String keyword, Alphabet alpha1, Alphabet alpha2) Initializes the AffineKey given a keyword and one or more alphabets.

Methods inherited from class hcrypto.cipher.HistoricalKey

getAlphabet, getBlocksize, getCipherKey, getCTAlphabet, getInstance, getKeyDescriptorPrompt, getKeyword, getPlainKey, initKey, initKey, invertKey, printAlphabets, removeDuplicateChars

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_KEY_DESCRIPTOR_PROMPT_STRING

public static final java.lang.String DEFAULT_KEY_DESCRIPTOR_PROMPT_STRING

A description for an Affine Key.

See Also:

Constant Field Values

DEFAULT_KEYWORD_STRING

public static final java.lang.String DEFAULT_KEYWORD_STRING

Default key values.

See Also:

Constant Field Values

Constructor Detail

AffineKey

public AffineKey()

Method Detail

init

public void init(java.lang.String keyspec)
          throws java.lang.Exception

Creates an AffineKey with the specified keyspec.

Specified by:

init in class HistoricalKey

Parameters:

keyspec - takes the form "integer,integer/alphabet", i.e. "5,21/az" for example, which would be mapped into the instance variables keyword as a String with the value "5,21", and alphabet as a String with the value "az".

Throws:

java.lang.Exception

init

public void init(java.lang.String keyword,
                 Alphabet alpha1,
                 Alphabet alpha2)
          throws java.lang.Exception

Initializes the AffineKey given a keyword and one or more alphabets.

Specified by:

init in class HistoricalKey

Parameters:

keyword - -- a string version of the keyword

alpha1, - alpha2 -- Alphabets for plain/ciphertext respectively. May be identical.

Throws:

java.lang.Exception

getAlgorithm

public java.lang.String getAlgorithm()

Returns the algorithm name "Affine".

Specified by:

getAlgorithm in class HistoricalKey

getKeyA

public int getKeyA()

Returns the keyA value for the Affine function.

getKeyB

public int getKeyB()

Returns the keyB value for the Affine function.