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.

==Diamong & Pearl usage==
<code>
filestream.Seek( 0xCF0E, SeekOrigin.Begin );
GetCheckSum( smallblock1 ); //small block 1
filestream.Seek( 0x1E2DE, SeekOrigin.Begin );
GetCheckSum( bigblock1 ); //big block 1
filestream.Seek( 0x4CF0E, SeekOrigin.Begin );
GetCheckSum( smallblock2 ); //small block 2
filestream.Seek( 0x5E2DE, SeekOrigin.Begin );
GetCheckSum( bigblock2 ); //big block 2
</code>

==Platinum usage==
<code>
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
</code>

==Determining the seeds==
<code>
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);
}
</code>
Also a static list can be used with the following values:
<code>
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
};
</code>

==Determining the checksum==
<code>
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;
}
</code>

Pokémon NDS Save File Checksum

2009-03-10T21:26:32Z

Sabresite: New page: Pokémon NDS uses a {{wplink|checksum|checksum}} at the footer each block in the save file to ensure consistent data. ==Diamong & Pearl usage== <code>...

Talk:Pokémon DP Save File Structure

2009-03-10T20:31:50Z

Sabresite: /* CheckSum Algorithm */

I just updated this page with slightly revised information on how the game determines which save blocks are most current. Turns out even Pokésav isn't programmed to pick up on an instance where both big blocks have the same ID number, which means my programs now read the save file more accurately than Pokésav. Interesting. --[[User:Codemonkey85|Codemonkey85]], 02/19/09 4:49 AM EST

Sabresite, I noticed your comment in the Bulbapedia page on the Pokémon NDS save file structure. I'm not terribly competent at wiki markup, so if you want to make either page look prettier, that's cool... as for content, would it be okay to copy the info from this page to the Bulbapedia one? I wrote both (with help from loadingNOW), so I don't see a problem, but I know you guys are trying to keep this wiki under wraps.

Also, I'd really like to add the save block checksum algorithms, but I can't really do it without either posting it in VB.Net (which everyone hates), or directly plagiarizing loadingNOW by posting it in C++. Unless there's a more language-independent way to format it.--[[User:Codemonkey85|Codemonkey85]], 02/26/09 12:22 PM EST

== CheckSum Algorithm ==

Please post the checksum algorithm in C++-like syntax. The code loadingNOW used was standard pseudo-language. [[User:Sabresite|Sabresite]] 20:44, 4 March 2009 (UTC)

So it's okay to use loadingNOW's example? Otherwise I'll just run my code in a converter and see what pops out. --[[User:Codemonkey85|Codemonkey85]] 12:01, 6 March 2009 (EST)

I am pretty sure loadingNOW would have no qualms with his code being posted. But we can always ask him. Of course, it might be a good idea to link to his document in a credits sections. [[User:SCV|SCV]] 17:43, 6 March 2009 (UTC)

[[LoadingNOW]] said its okay to use his document. We can also link to it so people can see the original. [[User:SCV|SCV]] 23:59, 7 March 2009 (UTC)
:This is now a moot point since we optimized a checksum algorithm for both games. What we should do is put it into a separate article, so that both DP/Platinum save file structure files can link to it.[[User:Sabresite|Sabresite]] 20:31, 10 March 2009 (UTC)

Talk:Pokémon NDS Save File Structure

2009-03-10T20:30:30Z

Sabresite: Talk:Pokémon NDS Save File Structure moved to Talk:Pokémon DP Save File Structure

#REDIRECT [[Talk:Pokémon DP Save File Structure]]

2009-03-06T09:30:13Z

Sabresite:

<table align="center" style="background: #FFCCCC; border: 2px solid #333333; width: 100%; -moz-border-radius: 30px;">
<tr><td align="center"><big>'''This article has inaccurate information.'''</big></td></tr>
{{ #if:{{{1}}}|<tr><td align="left">{{{1}}}</td></tr> }}
<tr><td align="center"><big>Help [[PP:About|Project Pokemon]] stay a useful resource by keeping this article accurate and up to date.</big></td></tr></table>
<includeonly>[[Category:Innacurate Articles]]</includeonly><noinclude>[[Category:Notice Templates]]</noinclude>