Sbox8x4.java
/*
* License : The MIT License
* Copyright(c) 2022 Olyutorskii
*/
package io.github.olyutorskii.aletojio.bijection;
import io.github.olyutorskii.aletojio.rng.RndInt32;
import java.util.Arrays;
import java.util.Objects;
/**
* S-box Bijection confusion.
*
* <p>Takes a 32-bit integer as input and outputs a confused 32-bit integer.
* Substitution is done in 8-bit units.
*
* <p>S-box of AES(Rijndael) is available.
* Any Sbox with 8bit-entry can be specified.
*
* <p>If there is a 1-bit change in the input,
* we can expect a 4-bit change from the output.
*
* @see <a href="https://en.wikipedia.org/wiki/S-box">
* S-box (Wikipedia)
* </a>
* @see <a href="https://en.wikipedia.org/wiki/Rijndael_S-box">
* Rijndael S-box (Wikipedia)
* </a>
* @see <a href="https://en.wikipedia.org/wiki/Confusion_and_diffusion">
* Confusion_and_diffusion (Wikipedia)
* </a>
* @see <a href="https://en.wikipedia.org/wiki/Substitution%E2%80%93permutation_network">
* Substitution-permutation network (SPN) (Wikipedia)
* </a>
*/
public class Sbox8x4 implements RndInt32 {
private static final int SIZE_SBOX = 256;
private static final int MASK_BYTE = (1 << Byte.SIZE) - 1;
// S-box table from AES.
// https://en.wikipedia.org/wiki/Rijndael_S-box
private static final int[] SBOX_RIJNDAEL = {
0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
};
private static final String ERRMSG_LENGTH = "S-box table must be 256 entry";
private static final String ERRMSG_BIJECTION = "S-box table must be bijection";
private final RndInt32 rnd;
private final int[] sbox = new int[SIZE_SBOX];
/**
* Constructor.
*
* <p>S-box of AES(Rijndael) is used.
*
* @param rndArg random source
* @throws NullPointerException argument is null
* @throws IllegalArgumentException invalid S-box
*/
public Sbox8x4(RndInt32 rndArg)
throws NullPointerException, IllegalArgumentException {
this(rndArg, SBOX_RIJNDAEL);
return;
}
/**
* Constructor.
*
* <p>S-box table length must be 256.
*
* <p>S-box table must be bijection. (minimal perfect hash function)
*
* <p>{@code (sboxArg[253] = 119)} means substitution from 253 to 119.
*
* @param rndArg random source
* @param sboxArg S-box table
* @throws NullPointerException argument is null
* @throws IllegalArgumentException invalid S-box
*/
public Sbox8x4(RndInt32 rndArg, int[] sboxArg)
throws NullPointerException, IllegalArgumentException {
super();
Objects.requireNonNull(rndArg);
Objects.requireNonNull(sboxArg);
this.rnd = rndArg;
checkSbox(sboxArg);
System.arraycopy(sboxArg, 0, this.sbox, 0, SIZE_SBOX);
return;
}
/**
* Map int value with Rijndael(AES) table.
*
* @param iVal int value
* @return mapped value
*/
public static int mapRijndael(int iVal) {
int result = mapTable(iVal, SBOX_RIJNDAEL);
return result;
}
/**
* Map int value with specified S-box table.
*
* <p>There is no bijection check.
*
* @param iVal int value
* @param table S-box table
* @return mapped value
* @throws NullPointerException table is null
* @throws IndexOutOfBoundsException table is too small
*/
public static int mapTable(int iVal, int[] table) {
int i0 = iVal & MASK_BYTE;
int i1 = (iVal >>> 8) & MASK_BYTE;
int i2 = (iVal >>> 16) & MASK_BYTE;
int i3 = (iVal >>> 24) & MASK_BYTE;
int o0 = table[i0];
int o1 = table[i1];
int o2 = table[i2];
int o3 = table[i3];
int result = (o3 << 24 | o2 << 16) | (o1 << 8 | o0);
return result;
}
/**
* Check S-box table.
*
* <p>S-box table length must be 256.
*
* <p>S-box table must be bijection. (minimal perfect hash function)
*
* <p>{@code (sboxArg[253] = 119)} means substitution from 253 to 119.
*
* @param sboxArg S-box table
* @throws NullPointerException null argument
* @throws IllegalArgumentException size unmatch or not bijection detected
*/
public static void checkSbox(int[] sboxArg)
throws NullPointerException, IllegalArgumentException {
Objects.requireNonNull(sboxArg);
if (sboxArg.length != SIZE_SBOX) {
throw new IllegalArgumentException(ERRMSG_LENGTH);
}
// checking minimal perfect hash function or not
int[] sorted = Arrays.copyOf(sboxArg, SIZE_SBOX);
Arrays.sort(sorted);
for (int src = 0; src < SIZE_SBOX; src++) {
int dst = sorted[src];
if (dst != src) {
throw new IllegalArgumentException(ERRMSG_BIJECTION);
}
}
return;
}
/**
* {@inheritDoc}
*
* @return {@inheritDoc}
*/
@Override
public int nextInt32() {
int iVal = this.rnd.nextInt32();
int result = mapTable(iVal, this.sbox);
return result;
}
}