I wrote an encryption application in C# which uses DES.
I wrote the encryption methods myself based on the DES algorithm description, not using the in-built methods for various reasons.
I checked it many times but still it still not working properly. It doesn't give back the original text after encryption and decryption.
I need ideas how can I find and correct the problem in my code!
I don't know what kind of bit array should i get after parts of encryption or decryption, so I can't locate the logical flaw in my code.
As last resort I could post/send my code, but I would be much happier if I could find the problem myself (based on your debugging ideas)!
UPDATE:
I don't want to use in built methods because I learn much more this way, and wanted to know if I like cryptographic programing or not...
public bool[] initialPermuation(bool[] sixtyfourbits)
{
bool[] bits = new bool[64];
int[] perm = new int[64]
{58, 50, 42, 34, 26, 18, 10, 2,
60, 52, 44, 36, 28, 20, 12, 4,
62, 54, 46, 38, 30, 22, 14, 6,
64, 56, 48, 40, 32, 24, 16, 8,
57, 49, 41, 33, 25, 17, 9, 1,
59, 51, 43, 35, 27, 19, 11, 3,
61, 53, 45, 37, 29, 21, 13, 5,
63, 55, 47, 39, 31, 23, 15, 7};
for (int i = 0; i < 64; i++)
{
bits[i] = sixtyfourbits[perm[i] - 1];
}
return bits;
}
public bool[] initialPermuationREV(bool[] sixtyfourbitsR)
{
bool[] bits = new bool[64];
int[] perm = new int[64]
{40, 8, 48, 16, 56, 24, 64, 32,
39, 7, 47, 15, 55, 23, 63, 31,
38, 6, 46, 14, 54, 22, 62, 30,
37, 5, 45, 13, 53, 21, 61, 29,
36, 4, 44, 12, 52, 20, 60, 28,
35, 3, 43, 11, 51, 19, 59, 27,
34, 2, 42, 10, 50, 18, 58, 26,
33, 1, 41, 9, 49, 17, 57, 25};
for (int i = 0; i < 64; i++)
{
bits[i] = sixtyfourbitsR[perm[i] - 1];
}
return bits;
}
private bool plusz(bool one, bool two)
{
bool end = false;
if (one || two) end = true;
if (one && two) end = false;
return end;
}
private bool[] plusz32(bool[] one, bool[] two)
{
for (int i = 0; i < 32; i++)
{
one[i] = plusz(one[i], two[i]);
}
return one;
}
private bool[] E32bitTO48(bool[] alap)
{
bool[] kimeno = new bool[48];
int[] perm = new int[48]
{32, 1, 2, 3, 4, 5,
4, 5, 6, 7, 8, 9,
8, 9, 10, 11, 12, 13,
12, 13, 14, 15, 16, 17,
16, 17, 18, 19, 20, 21,
20, 21, 22, 23, 24, 25,
24, 25, 26, 27, 28, 29,
28, 29, 30, 31, 32, 1};
for (int i = 0; i < 48; i++)
{
kimeno[i] = alap[perm[i] - 1];
}
return kimeno;
}
private bool[] permutation32bit(bool[] alap)
{
bool[] bits = new bool[32];
int[] perm = new int[32]
{16, 7, 20, 21,
29, 12, 28, 17,
1, 15, 23, 26,
5, 18, 31, 10,
2, 8, 24, 14,
32, 27, 3, 9,
19, 13, 30, 6,
22, 11, 4, 25};
for (int i = 0; i < 32; i++)
{
bits[i] = alap[perm[i] - 1];
}
return bits;
}
private bool[] permutation1Key(bool[] alap, out bool[] keyD)
{
keyD = new bool[28];
bool[] bits = new bool[28];
int[] perm = new int[28]
{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};
int[] perm2 = new int[28]
{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};
for (int i = 0; i < 28; i++)
{
bits[i] = alap[perm[i] - 1];
}
for (int i = 0; i < 28; i++)
{
keyD[i] = alap[perm2[i] - 1];
}
return bits;
}
private bool[] permutation2Key(bool[] alap1, bool[] alap2)
{
bool[] summ = new bool[56];
bool[] bits = new bool[48];
for (int i = 0; i < 28; i++)
{
summ[i] = alap1[i];
summ[28 + i] = alap2[i];
}
int[] perm = new int[48]
{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};
for (int i = 0; i < 48; i++)
{
bits[i] = summ[perm[i] - 1];
}
return bits;
}
private bool[] leftShift(int szam, bool[] alap)
{
bool[] bits = new bool[alap.Length];
int z = shifts[szam - 1];
for (int j = 0; j < z; j++)
{
for (int i = 0; i < alap.Length; i++)
{
if (i != alap.Length - 1) bits[i] = alap[i + 1];
else bits[i] = alap[0];
}
}
return bits;
}
private int sSelection(bool[] alap, out int second)
{
int ki = 0;
second = 0;
if (alap[0]) ki = ki + 2;
if (alap[5]) ki = ki + 1;
if (alap[1]) second = second + 8;
if (alap[2]) second = second + 4;
if (alap[3]) second = second + 2;
if (alap[4]) second = second + 1;
return ki;
}
private bool[] sAddOut(int xy)
{
bool[] bits = new bool[4];
if (xy >= 8)
{
bits[0] = true;
xy = xy - 8;
}
else bits[0] = false;
if (xy >= 4)
{
bits[1] = true;
xy = xy - 4;
}
else bits[1] = false;
if (xy >= 2)
{
bits[2] = true;
xy = xy - 2;
}
else bits[2] = false;
if (xy >= 1)
{
bits[3] = true;
xy = xy - 1;
}
else bits[3] = false;
return bits;
}
private bool[] KeyGeneration(int KeyN)
{
if (txtkey.Text == "" || txtkey.Text.Length != 8) MessageBox.Show("Nem megfelelő kulcs!");
char[] kulcs = txtkey.Text.ToCharArray();
bool[] kulcsbits = chartoBool(kulcs);
bool[] Dn;
bool[] Cn = permutation1Key(kulcsbits, out Dn);
for (int i = 0; i < KeyN; i++)
{
Cn = leftShift(i + 1, Cn);
Dn = leftShift(i + 1, Dn);
}
bool[] bits = permutation2Key(Cn, Dn);
return bits;
}
private bool[] fScrpyt(bool[] alapX, bool[] KulcsN)
{
bool[] bits = new bool[48];
bits = E32bitTO48(alapX);
for (int i = 0; i < 48; i++)
{
bits[i] = plusz(bits[i], KulcsN[i]);
}
bool[][] bitA = new bool[8][];
bool[][] bitA2 = new bool[8][];
for (int i = 0; i < 8; i++)
{
bitA[i] = new bool[6];
for (int j = 0; j < 6; j++)
{
bitA[i][j] = bits[j + i * 6];
}
}
int Sx, Sy;
Sx = sSelection(bitA[0], out Sy);
bitA2[0] = sAddOut(S1[Sx, Sy]);
Sx = sSelection(bitA[1], out Sy);
bitA2[1] = sAddOut(S2[Sx, Sy]);
Sx = sSelection(bitA[2], out Sy);
bitA2[2] = sAddOut(S3[Sx, Sy]);
Sx = sSelection(bitA[3], out Sy);
bitA2[3] = sAddOut(S4[Sx, Sy]);
Sx = sSelection(bitA[4], out Sy);
bitA2[4] = sAddOut(S5[Sx, Sy]);
Sx = sSelection(bitA[5], out Sy);
bitA2[5] = sAddOut(S6[Sx, Sy]);
Sx = sSelection(bitA[6], out Sy);
bitA2[6] = sAddOut(S7[Sx, Sy]);
Sx = sSelection(bitA[7], out Sy);
bitA2[7] = sAddOut(S8[Sx, Sy]);
bool[] thirtytwo = new bool[32];
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 4; j++)
{
thirtytwo[i * 4 + j] = bitA2[i][j];
}
}
return permutation32bit(thirtytwo);
}
private bool[] seperate(bool[] alap, out bool[] second)
{
bool[] bits = new bool[32];
second = new bool[32];
for (int i = 0; i < 32; i++)
{
bits[i] = alap[i];
}
for (int i = 0; i < 32; i++)
{
second[i] = alap[32 + i];
}
return bits;
}
private bool[] pluszbool64(bool[] one, bool[] two)
{
bool[] all = new bool[64];
for (int i = 0; i < 32; i++)
{
all[i] = one[i];
}
for (int i = 0; i < 32; i++)
{
all[32 + i] = two[i];
}
return all;
}
private bool[] Encrpytion(bool[] textbits)
{
int hossz = textbits.Length / 64;
bool[] bits = new bool[64];
for (int i = 0; i < hossz; i++)
{
for (int j = 0; j < 64; j++)
{
bits[j] = textbits[j + i * 64];
}
bits = initialPermuation(bits);
bool[] left = new bool[32];
bool[] right = new bool[32];
bool[] leftN = new bool[32];
bool[] rightN = new bool[32];
left = seperate(bits, out right);
for (int ii = 0; ii < 16; ii++)
{
leftN = right;
rightN = plusz32(left, fScrpyt(right, KeyGeneration(ii + 1)));
left = leftN;
right = rightN;
}
bits = pluszbool64(right, left);
}
return initialPermuationREV(bits);
}
private bool[] Decrpytion(bool[] textbits)
{
int hossz = textbits.Length / 64;
bool[] bits = new bool[64];
for (int i = 0; i < hossz; i++)
{
for (int j = 0; j < 64; j++)
{
bits[j] = textbits[j + i * 64];
}
bits = initialPermuationREV(bits);
bool[] left = new bool[32];
bool[] right = new bool[32];
bool[] leftN = new bool[32];
bool[] rightN = new bool[32];
left = seperate(bits, out right);
leftN = left;
left = right;
right = leftN;
for (int ii = 16; ii > 0; ii--)
{
rightN = left;
leftN = plusz32(right, fScrpyt(left, KeyGeneration(ii)));
left = leftN;
right = rightN;
}
bits = pluszbool64(right, left);
}
return initialPermuation(bits);
}
int[,] S1 = new int[4, 16] {
{ 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7},
{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}};
int[,] S2 = new int[4, 16]
{{15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10},
{2, 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}};
int[,] S3 = new int[4, 16]
{{10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8},
{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}};
int[,] S4 = new int[4, 16]
{{7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15},
{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}};
int[,] S5 = new int[4, 16]
{{2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9},
{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}};
int[,] S6 = new int[4, 16]
{{10, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11},
{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}};
int[,] S7 = new int[4, 16]
{{4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1},
{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}};
int[,] S8 = new int[4, 16]
{{13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7},
{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}};
int[] shifts = new int[16] { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };