rabbitescape.engine.util.MegaCoder Class Reference

Static Public Member Functions
static String	encode (String input)
static String	decode (String input)

Private Member Functions
	MegaCoder ()

Static Private Member Functions
static char[]	getSortedUniqueChars (char[] charArray)
static char[]	replaceUsingCharacterList (char[] charsListKey, char[] input)
static char[]	exchangeCharacters (char[] chars, char a, char b)
static char[]	shuffle (char[] input, int key)
static char[]	copyArray (char[] input)

Static Private Attributes
static final char[]	COMMON_CHARACTERS

Detailed Description

Obfuscate strings like a champion.

Swaps characters within the string around, swaps well-known characters with each other, and transposes the string by exchanging characters with other characters.

The MegaCoder is licensed here for use as part of rabbit-escape, but is also declared public domain, so that it may be used, without attribution, by anyone who needs obfuscation slightly more powerful than rot13, but less portable than base64. (For clarity, the MegaCoder is this single file).

The MegaCoder shuffle algorithm:

Input: An array of length l, A integer key k
i = 0
while at least two array entries remain unswapped:
  if array entry i has not been swapped:
    j = (floor(length / 2) + 3i + k) mod l
    while array entry j has already been swapped:
      j = (j + 1) mod l
    swap entries i and j in the array
  i = i + 1
Output: The modified array

The MegaCoder replace algorithm:

Input: An key array k of length l, An array of characters x
for i in [0, floor(l / 2)]:
  a = entry i in k; b = entry (l - 1 - i) in k
  replace all instances of a with b, and b with a, in the array x
Output: The modified array x

The MegaCoder uniquify algorithm:

Input: An array of characters x
Output: The set of characters in x sorted by value

The MegaCoder encode algorithm:

Input: An array of characters x of length l
k1 = uniquify(x)
x = replace(k1, x)
k2 = shuffle(C, l) where C is the array of ASCII characters from space (0x20) to tilde (0x7e)
x = replace(k2, x)
x = shuffle(x, 0)
Output: The modified array x

The MegaCoder decode algorithm:

Input: An array of characters x of length l
x = shuffle(x, 0)
k2 = shuffle(C, l) where C is the array of ASCII characters from space (0x20) to tilde (0x7e)
x = replace(k2, x)
k1 = uniquify(x)
x = replace(k1, x)
Output: The modified array x

Author

tttppp

Constructor & Destructor Documentation

rabbitescape.engine.util.MegaCoder.MegaCoder ( )

private

Private constructor for util class.

Member Function Documentation

static char [] rabbitescape.engine.util.MegaCoder.copyArray ( char[]  input )

staticprivate

static String rabbitescape.engine.util.MegaCoder.decode ( String  input )

static

Decode a string using the MegaCoder obfuscation routine.

Parameters

input

The ciphertext to decode.

Returns

The plaintext.

static String rabbitescape.engine.util.MegaCoder.encode ( String  input )

static

Encode a string using the MegaCoder obfuscation routine.

Parameters

input

The plaintext to encode.

Returns

The obfuscated ciphertext.

static char [] rabbitescape.engine.util.MegaCoder.exchangeCharacters ( char[]  chars, char  a, char  b  )

staticprivate

Swap two characters with each other in a given characters list.

Parameters

chars	The list of characters to search through.
a	A character.
b	Another character.

Returns

The input, but with all occurrences of a and b exchanged.

static char [] rabbitescape.engine.util.MegaCoder.getSortedUniqueChars ( char[]  charArray )

staticprivate

Create a new character array containing every character that appears in a given array once. The new array will be sorted by natural order.

Parameters

charArray

The character array to process.

Returns

An array containing the sorted set of characters in the input.

static char [] rabbitescape.engine.util.MegaCoder.replaceUsingCharacterList ( char[]  charsListKey, char[]  input  )

staticprivate

Replace characters in a string using a key.

Parameters

charsListKey	A list of distinct characters. The first will be swapped with the last, and so on. If there is an odd number of characters then the middle character will not be swapped at all.
input	The string to replace the characters in.

static char [] rabbitescape.engine.util.MegaCoder.shuffle ( char[]  input, int  key  )

staticprivate

Shuffle the characters in the given string.

Parameters

input	The string to be shuffled.
key	A value that changes the shuffling algorithm.

Returns

The string with letters swapped around a bit.

Member Data Documentation

final char [] rabbitescape.engine.util.MegaCoder.COMMON_CHARACTERS

staticprivate

Initial value:

= new char[] {
        ' ', '!', '"', '#', '$', '%', '&',
        '\'', '(', ')', '*', '+', ',',
        '-', '.', '/', '0', '1', '2', '3',
        '4', '5', '6', '7', '8', '9', ':',
        ';', '<', '=', '>', '?', '@', 'A',
        'B', 'C', 'D', 'E', 'F', 'G', 'H',
        'I', 'J', 'K', 'L', 'M', 'N', 'O',
        'P', 'Q', 'R', 'S', 'T', 'U', 'V',
        'W', 'X', 'Y', 'Z', '[', '\\',
        ']', '^', '_', '`', 'a', 'b', 'c',
        'd', 'e', 'f', 'g', 'h', 'i', 'j',
        'k', 'l', 'm', 'n', 'o', 'p', 'q',
        'r', 's', 't', 'u', 'v', 'w', 'x',
        'y', 'z', '{', '|', '}', '~' }

A list of common ASCII characters that can be swapped with each other.

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The documentation for this class was generated from the following file:

• rabbit-escape-engine/src/rabbitescape/engine/util/MegaCoder.java