Figure 5 Cipher Algorithm PseudocodeCipher(byte[] input, byte[] output)
{
byte[4,4] State;
copy input[] into State[]
AddRoundKey
for (round = 1; round < Nr-1; ++round)
{
SubBytes
ShiftRows
MixColumns
AddRoundKey
}
SubBytes
ShiftRows
AddRoundKey
copy State[] to output[]
}
Figure 7 Initializing Rcon private void BuildRcon()
{
this.Rcon = new byte[11,4] { {0x00, 0x00, 0x00, 0x00},
{0x01, 0x00, 0x00, 0x00},
{0x02, 0x00, 0x00, 0x00},
{0x04, 0x00, 0x00, 0x00},
{0x08, 0x00, 0x00, 0x00},
{0x10, 0x00, 0x00, 0x00},
{0x20, 0x00, 0x00, 0x00},
{0x40, 0x00, 0x00, 0x00},
{0x80, 0x00, 0x00, 0x00},
{0x1b, 0x00, 0x00, 0x00},
{0x36, 0x00, 0x00, 0x00} };
} // BuildRcon()
Figure 8 SetNbNkNr Method private void SetNbNkNr(KeySize keySize)
{
this.Nb = 4;
if (keySize == KeySize.Bits128)
{
this.Nk = 4;
this.Nr = 10;
}
else if (keySize == KeySize.Bits192)
{
this.Nk = 6;
this.Nr = 12;
}
else if (keySize == KeySize.Bits256)
{
this.Nk = 8;
this.Nr = 14;
}
} // SetNbNkNr()
Figure 9 Sbox Initialization private void BuildSbox()
{
this.Sbox = new byte[16,16] { // populate the Sbox matrix
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/*0*/ {0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76},
/*1*/ {0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0},
/*2*/ {0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15},
/*3*/ {0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75},
/*4*/ {0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84},
/*5*/ {0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf},
/*6*/ {0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8},
/*7*/ {0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2},
/*8*/ {0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73},
/*9*/ {0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb},
/*a*/ {0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79},
/*b*/ {0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08},
/*c*/ {0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a},
/*d*/ {0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e},
/*e*/ {0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf},
/*f*/ {0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16} };
} // BuildSbox()
Figure 10 KeyExpansion Method private void KeyExpansion()
{
this.w = new byte[Nb * (Nr+1), 4];
for (int row = 0; row < Nk; ++row)
{
this.w[row,0] = this.key[4*row];
this.w[row,1] = this.key[4*row+1];
this.w[row,2] = this.key[4*row+2];
this.w[row,3] = this.key[4*row+3];
}
byte[] temp = new byte[4];
for (int row = Nk; row < Nb * (Nr+1); ++row)
{
temp[0] = this.w[row-1,0]; temp[1] = this.w[row-1,1];
temp[2] = this.w[row-1,2]; temp[3] = this.w[row-1,3];
if (row % Nk == 0)
{
temp = SubWord(RotWord(temp));
temp[0] = (byte)( (int)temp[0] ^ (int)this.Rcon[row/Nk,0] );
temp[1] = (byte)( (int)temp[1] ^ (int)this.Rcon[row/Nk,1] );
temp[2] = (byte)( (int)temp[2] ^ (int)this.Rcon[row/Nk,2] );
temp[3] = (byte)( (int)temp[3] ^ (int)this.Rcon[row/Nk,3] );
}
else if ( Nk > 6 && (row % Nk == 4) )
{
temp = SubWord(temp);
}
// w[row] = w[row-Nk] xor temp
this.w[row,0] = (byte) ( (int)this.w[row-Nk,0] ^ (int)temp[0] );
this.w[row,1] = (byte) ( (int)this.w[row-Nk,1] ^ (int)temp[1] );
this.w[row,2] = (byte) ( (int)this.w[row-Nk,2] ^ (int)temp[2] );
this.w[row,3] = (byte) ( (int)this.w[row-Nk,3] ^ (int)temp[3] );
} // for loop
} // KeyExpansion()
Figure 11 The Cipher Method public void Cipher(byte[] input, byte[] output)
{
// state = input
this.State = new byte[4,Nb];
for (int i = 0; i < (4 * Nb); ++i)
{
this.State[i % 4, i / 4] = input[i];
}
AddRoundKey(0);
for (int round = 1; round <= (Nr - 1); ++round)
{
SubBytes();
ShiftRows();
MixColumns();
AddRoundKey(round);
}
SubBytes();
ShiftRows();
AddRoundKey(Nr);
// output = state
for (int i = 0; i < (4 * Nb); ++i)
{
output[i] = this.State[i % 4, i / 4];
}
} // Cipher()
Figure 12 AddRoundKey and SubBytes Methods private void AddRoundKey(int round)
{
for (int r = 0; r < 4; ++r)
{
for (int c = 0; c < 4; ++c)
{
this.State[r,c] = (byte) ( (int)this.State[r,c] ^
(int)w[(round*4)+c,r] );
}
}
} // AddRoundKey()
private void SubBytes()
{
for (int r = 0; r < 4; ++r)
{
for (int c = 0; c < 4; ++c)
{
this.State[r,c] = this.Sbox[ (this.State[r,c] >> 4),
(this.State[r,c] & 0x0f) ];
}
}
} // SubBytes
Figure 13 ShiftRows Method private void ShiftRows()
{
byte[,] temp = new byte[4,4];
for (int r = 0; r < 4; ++r)
{
for (int c = 0; c < 4; ++c)
{
temp[r,c] = this.State[r,c];
}
}
for (int r = 1; r < 4; ++r) //
{
for (int c = 0; c < 4; ++c)
{
this.State[r,c] = temp[ r, (c + r) % Nb ];
}
}
} // ShiftRows()
Figure 14 MixColumns Method private void MixColumns()
{
byte[,] temp = new byte[4,4];
for (int r = 0; r < 4; ++r)
{
for (int c = 0; c < 4; ++c)
{
temp[r,c] = this.State[r,c];
}
}
for (int c = 0; c < 4; ++c)
{
this.State[0,c] = (byte) ( (int)gfmultby02(temp[0,c]) ^
(int)gfmultby03(temp[1,c]) ^
(int)gfmultby01(temp[2,c]) ^
(int)gfmultby01(temp[3,c]) );
this.State[1,c] = (byte) ( (int)gfmultby01(temp[0,c]) ^
(int)gfmultby02(temp[1,c]) ^
(int)gfmultby03(temp[2,c]) ^
(int)gfmultby01(temp[3,c]) );
this.State[2,c] = (byte) ( (int)gfmultby01(temp[0,c]) ^
(int)gfmultby01(temp[1,c]) ^
(int)gfmultby02(temp[2,c]) ^
(int)gfmultby03(temp[3,c]) );
this.State[3,c] = (byte) ( (int)gfmultby03(temp[0,c]) ^
(int)gfmultby01(temp[1,c]) ^
(int)gfmultby01(temp[2,c]) ^
(int)gfmultby02(temp[3,c]) );
}
} // MixColumns
Figure 15 Using AES static void Main(string[] args)
{
byte[] plainText = new byte[] {0x00, 0x11, 0x22, 0x33, 0x44, 0x55,
0x66, 0x77,0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff};
byte[] cipherText = new byte[16];
byte[] decipheredText = new byte[16];
byte[] keyBytes = new byte[] {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
0x07,0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,0x10, 0x11,
0x12, 0x13, 0x14, 0x15, 0x16, 0x17};
Aes a = new Aes(Aes.KeySize.Bits192, keyBytes);
Console.WriteLine("\nAdvanced Encryption System Demo in .NET");
Console.WriteLine("\nThe plaintext is: ");
DisplayAsBytes(plainText);
Console.WriteLine("\nUsing a " + Aes.KeySize.Bits192.ToString() +
"-key of: ");
DisplayAsBytes(keyBytes);
a.Cipher(plainText, cipherText);
Console.WriteLine("\nThe resulting ciphertext is: ");
DisplayAsBytes(cipherText);
a.InvCipher(cipherText, decipheredText);
Console.WriteLine("\nAfter deciphering the ciphertext, the result
is: ");
DisplayAsBytes(decipheredText);
Console.WriteLine("\nDone");
Console.ReadLine();
} // Main()
static void DisplayAsBytes(byte[] bytes)
{
for (int i = 0; i < bytes.Length; ++i)
{
Console.Write(bytes[i].ToString("x2") + " " );
if (i > 0 && i % 16 == 0) Console.Write("\n");
}
Console.WriteLine("");
} // DisplayAsBytes()
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