Pokémon NDS Save File Checksum: Difference between revisions

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Pokémon NDS uses a {{wplink|checksum|checksum}} at the footer each block in the [[Pokémon NDS Save File Structure|save file]] to ensure consistent data.
Pokémon NDS uses a {{wplink|checksum|checksum}} at the footer each block in the [[Pokémon NDS Save File Structure|save file]] to ensure consistent data.


==Diamond & Pearl usage==
==Diamond & Pearl usage==
<code>
<code>
  filestream.Seek( 0xC0FE, SeekOrigin.Begin );
  filestream.Seek( 0xC0FE, SeekOrigin.Begin );
  GetCheckSum( smallblock1 ); //small block 1
  GetCheckSum( smallblock1 ); //small block 1
Line 12: Line 11:
  filestream.Seek( 0x5E2DE, SeekOrigin.Begin );
  filestream.Seek( 0x5E2DE, SeekOrigin.Begin );
  GetCheckSum( bigblock2 ); //big block 2
  GetCheckSum( bigblock2 ); //big block 2
&lt;/code&gt;
</code>


==Platinum usage==
==Platinum usage==
&lt;code&gt;
<code>
  filestream.Seek( 0xCF2A, SeekOrigin.Begin );
  filestream.Seek( 0xCF2A, SeekOrigin.Begin );
  GetCheckSum( smallblock1 ); //small block 1
  GetCheckSum( smallblock1 ); //small block 1
Line 24: Line 23:
  filestream.Seek( 0x5F10E, SeekOrigin.Begin );
  filestream.Seek( 0x5F10E, SeekOrigin.Begin );
  GetCheckSum( bigblock2 ); //big block 2
  GetCheckSum( bigblock2 ); //big block 2
&lt;/code&gt;
</code>


==Determining the seeds==
==Determining the seeds==
&lt;code&gt;
<code>
  public static int[] SeedTable;
  public static int[] SeedTable;
   
   
Line 39: Line 38:
  do
  do
  {
  {
  result = index &lt;&lt; 8;
  result = index << 8;
  int index2 = 0;
  int index2 = 0;
  do
  do
  {
  {
  if (((byte)(result&gt;&gt;8) &amp; 0x80)!=0)
  if (((byte)(result>>8) & 0x80)!=0)
  result = (2 * result )^ 0x1021;
  result = (2 * result )^ 0x1021;
  else
  else
  result *= 2;
  result *= 2;
  }
  }
  while (++index &lt; 8);
  while (++index < 8);
   
   
  seeds[index++] = (ushort)(result);
  seeds[index++] = (ushort)(result);
  } while (index &lt;= 0xFF);
  } while (index <= 0xFF);
  }
  }
&lt;/code&gt;
</code>
Also a static list can be used with the following values:
Also a static list can be used with the following values:
&lt;code&gt;
<code>
  public static readonly int[] SeedTable = new int[]
  public static readonly int[] SeedTable = new int[]
  {
  {
Line 91: Line 90:
  0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
  0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
  };
  };
&lt;/code&gt;
</code>


==Determining the checksum==
==Determining the checksum==
*''data'' is a byte array for a small block or big block.
*''data'' is a byte array for a small block or big block.
&lt;code&gt;
<code>
  public ushort GetCheckSum( byte[] data )
  public ushort GetCheckSum( byte[] data )
  {
  {
  int sum = 0xFFFF;
  int sum = 0xFFFF;
   
   
  for ( int i = 0; i &lt; data.Length; i++ )
  for ( int i = 0; i < data.Length; i++ )
  sum = (sum &lt;&lt; 8) ^ SeedTable[ (byte)(data[i] ^ (byte)(sum&gt;&gt;8)) ];
  sum = (sum << 8) ^ SeedTable[ (byte)(data[i] ^ (byte)(sum>>8)) ];
   
   
  return (ushort)sum;
  return (ushort)sum;
  }
  }
&lt;/code&gt;
</code>

Revision as of 04:41, 27 November 2010

Pokémon NDS uses a checksum at the footer each block in the save file to ensure consistent data.

Diamond & Pearl usage

filestream.Seek( 0xC0FE, SeekOrigin.Begin );
GetCheckSum( smallblock1 ); //small block 1
filestream.Seek( 0x1E2DE, SeekOrigin.Begin );
GetCheckSum( bigblock1 ); //big block 1
filestream.Seek( 0x4C0FE, SeekOrigin.Begin );
GetCheckSum( smallblock2 ); //small block 2
filestream.Seek( 0x5E2DE, SeekOrigin.Begin );
GetCheckSum( bigblock2 ); //big block 2

Platinum usage

filestream.Seek( 0xCF2A, SeekOrigin.Begin );
GetCheckSum( smallblock1 ); //small block 1
filestream.Seek( 0x1F10E, SeekOrigin.Begin );
GetCheckSum( bigblock1 ); //big block 1
filestream.Seek( 0x4CF2A, SeekOrigin.Begin );
GetCheckSum( smallblock2 ); //small block 2
filestream.Seek( 0x5F10E, SeekOrigin.Begin );
GetCheckSum( bigblock2 ); //big block 2

Determining the seeds

		public static int[] SeedTable;

		public static void GetSeeds()
		{
			SeedTable = new int[0x100];

			int index = 0;
			int result = 0;

			do
			{
				result = index << 8;
				int index2 = 0;
				do
				{
					if (((byte)(result>>8) & 0x80)!=0)
						result = (2 * result )^ 0x1021;
					else
						result *= 2;
				}
				while (++index < 8);

				seeds[index++] = (ushort)(result);
			} while (index <= 0xFF);
		}

Also a static list can be used with the following values:

		public static readonly int[] SeedTable = new int[]
			{
				0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
				0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
				0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
				0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
				0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
				0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
				0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
				0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
				0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
				0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
				0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
				0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
				0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
				0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
				0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
				0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
				0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
				0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
				0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
				0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
				0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
				0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
				0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
				0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
				0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
				0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
				0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
				0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
				0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
				0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
				0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
				0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
			};

Determining the checksum

  • data is a byte array for a small block or big block.

		public ushort GetCheckSum( byte[] data )
		{
			int sum = 0xFFFF;

			for ( int i = 0; i < data.Length; i++ )
				sum = (sum << 8) ^ SeedTable[ (byte)(data[i] ^ (byte)(sum>>8)) ];

			return (ushort)sum;
		}