Package io.github.olyutorskii.aletojio.bijection

Class Sbox8x4

java.lang.Object

io.github.olyutorskii.aletojio.bijection.Sbox8x4

All Implemented Interfaces:

RndInt32

public class Sbox8x4
extends Object
implements RndInt32

S-box Bijection confusion.

Takes a 32-bit integer as input and outputs a confused 32-bit integer. Substitution is done in 8-bit units.

S-box of AES(Rijndael) is available. Any Sbox with 8bit-entry can be specified.

If there is a 1-bit change in the input, we can expect a 4-bit change from the output.

See Also:

• S-box (Wikipedia)
• Rijndael S-box (Wikipedia)
• Confusion_and_diffusion (Wikipedia)
• Substitution-permutation network (SPN) (Wikipedia)

Constructor Summary

Constructors

Constructor	Description
Sbox8x4(RndInt32 rndArg)	Constructor.
Sbox8x4(RndInt32 rndArg, int[] sboxArg)	Constructor.

Method Summary

Modifier and Type	Method	Description
static void	checkSbox(int[] sboxArg)	Check S-box table.
static int	mapRijndael(int iVal)	Map int value with Rijndael(AES) table.
static int	mapTable(int iVal, int[] table)	Map int value with specified S-box table.
int	nextInt32()	Return next random number as 32bit int with random sign-bit.

Methods inherited from class java.lang.Object

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

Constructor Details

Sbox8x4

public Sbox8x4(RndInt32 rndArg)
        throws NullPointerException,
IllegalArgumentException

Constructor.

S-box of AES(Rijndael) is used.

Parameters:

rndArg - random source

Throws:

NullPointerException - argument is null

IllegalArgumentException - invalid S-box

Sbox8x4

public Sbox8x4(RndInt32 rndArg,
 int[] sboxArg)
        throws NullPointerException,
IllegalArgumentException

Constructor.

S-box table length must be 256.

S-box table must be bijection. (minimal perfect hash function)

(sboxArg[253] = 119) means substitution from 253 to 119.

Parameters:

rndArg - random source

sboxArg - S-box table

Throws:

NullPointerException - argument is null

IllegalArgumentException - invalid S-box

Method Details

mapRijndael

public static int mapRijndael(int iVal)

Map int value with Rijndael(AES) table.

Parameters:

iVal - int value

Returns:

mapped value

mapTable

public static int mapTable(int iVal,
 int[] table)

Map int value with specified S-box table.

There is no bijection check.

Parameters:

iVal - int value

table - S-box table

Returns:

mapped value

Throws:

NullPointerException - table is null

IndexOutOfBoundsException - table is too small

checkSbox

public static void checkSbox(int[] sboxArg)
                      throws NullPointerException,
IllegalArgumentException

Check S-box table.

S-box table length must be 256.

S-box table must be bijection. (minimal perfect hash function)

(sboxArg[253] = 119) means substitution from 253 to 119.

Parameters:

sboxArg - S-box table

Throws:

NullPointerException - null argument

IllegalArgumentException - size unmatch or not bijection detected

nextInt32

public int nextInt32()

Return next random number as 32bit int with random sign-bit.

Specified by:

nextInt32 in interface RndInt32

Returns:

random number