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DES Algorithm - Java Implementation
Part:
1
2
3
4
(Continued from previous part...)
private static byte[] doXORBytes(byte[] a, byte[] b) {
byte[] out = new byte[a.length];
for (int i=0; i<a.length; i++) {
out[i] = (byte) (a[i] ^ b[i]);
}
return out;
}
static final int[] S = {
14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7, // S1
0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13,
15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10, // S2
3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9,
10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8, // S3
13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12,
7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15, // S4
13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14,
2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9, // S5
14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3,
12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11, // S6
10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13,
4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1, // S7
13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12,
13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7, // S8
1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11
};
private static byte[] substitution6x4(byte[] in) {
in = splitBytes(in,6); // Splitting byte[] into 6-bit blocks
byte[] out = new byte[in.length/2];
int lhByte = 0;
for (int b=0; b<in.length; b++) { // Should be sub-blocks
byte valByte = in[b];
int r = 2*(valByte>>7&0x0001)+(valByte>>2&0x0001); // 1 and 6
int c = valByte>>3&0x000F; // Middle 4 bits
int hByte = S[64*b+16*r+c]; // 4 bits (half byte) output
if (b%2==0) lhByte = hByte; // Left half byte
else out[b/2] = (byte) (16*lhByte + hByte);
}
return out;
}
private static byte[] splitBytes(byte[] in, int len) {
int numOfBytes = (8*in.length-1)/len + 1;
byte[] out = new byte[numOfBytes];
for (int i=0; i<numOfBytes; i++) {
for (int j=0; j<len; j++) {
int val = getBit(in, len*i+j);
setBit(out,8*i+j,val);
}
}
return out;
}
static final int[] PC1 = {
57, 49, 41, 33, 25, 17, 9,
1, 58, 50, 42, 34, 26, 18,
10, 2, 59, 51, 43, 35, 27,
19, 11, 3, 60, 52, 44, 36,
63, 55, 47, 39, 31, 23, 15,
7, 62, 54, 46, 38, 30, 22,
14, 6, 61, 53, 45, 37, 29,
21, 13, 5, 28, 20, 12, 4
};
static final int[] PC2 = {
14, 17, 11, 24, 1, 5,
3, 28, 15, 6, 21, 10,
23, 19, 12, 4, 26, 8,
16, 7, 27, 20, 13, 2,
41, 52, 31, 37, 47, 55,
30, 40, 51, 45, 33, 48,
44, 49, 39, 56, 34, 53,
46, 42, 50, 36, 29, 32
};
static final int[] SHIFTS = {
1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
};
public static byte[][] getSubkeys(byte[] theKey)
throws Exception {
int activeKeySize = PC1.length;
int numOfSubKeys = SHIFTS.length;
byte[] activeKey = selectBits(theKey,PC1);
int halfKeySize = activeKeySize/2;
byte[] c = selectBits(activeKey,0,halfKeySize);
byte[] d = selectBits(activeKey,halfKeySize,halfKeySize);
byte[][] subKeys = new byte[numOfSubKeys][];
for (int k=0; k<numOfSubKeys; k++) {
c = rotateLeft(c,halfKeySize,SHIFTS[k]);
d = rotateLeft(d,halfKeySize,SHIFTS[k]);
byte[] cd = concatenateBits(c,halfKeySize,d,halfKeySize);
subKeys[k] = selectBits(cd,PC2);
}
return subKeys;
}
private static byte[] rotateLeft(byte[] in, int len, int step) {
int numOfBytes = (len-1)/8 + 1;
byte[] out = new byte[numOfBytes];
for (int i=0; i<len; i++) {
int val = getBit(in,(i+step)%len);
setBit(out,i,val);
}
return out;
}
private static byte[] concatenateBits(byte[] a, int aLen, byte[] b,
int bLen) {
int numOfBytes = (aLen+bLen-1)/8 + 1;
byte[] out = new byte[numOfBytes];
int j = 0;
for (int i=0; i<aLen; i++) {
int val = getBit(a,i);
setBit(out,j,val);
j++;
}
for (int i=0; i<bLen; i++) {
int val = getBit(b,i);
setBit(out,j,val);
j++;
}
return out;
}
(Continued on next part...)
Part:
1
2
3
4
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