Kernel/XcDESKeyParity - Revision history

JayFoxRox at 00:03, 3 October 2018

2018-10-03T00:03:27Z

JayFoxRox at 23:58, 2 October 2018

2018-10-02T23:58:44Z

JayFoxRox: Port from my Python code, but with added comments

2018-10-02T23:56:38Z

Port from my Python code, but with added comments

New page

=== Pseudocode ===

<pre>
XBAPI VOID NTAPI XcDESKeyParity(IN OUT PUCHAR pbKey, IN ULONG dwKeyLength) {

// For each number between 0x0 and 0xF, this tells how many set bits there are.
const uint8_t parity_table[] = {
0x00, 0x01, 0x01, 0x02, 0x01, 0x02, 0x02, 0x03,
0x01, 0x02, 0x02, 0x03, 0x02, 0x03, 0x03, 0x04
};

// Count number of set bits in each byte, and flip the lowest bit if there's an even number.
// This forces each byte to have odd parity, as required by DES.
for(ULONG i = 0; i < dwKeyLength; i++) {
high_parity = parity_table[(pbKey[i] >> 4) & 0xF];
low_parity = parity_table[(pbKey[i] >> 0) & 0xF];
if ((high_parity + low_parity) % 2) == 0 {
pbKey[i] ^= 0x01;
}
}

return;
}
</pre>

@@ Line 1: / Line 1: @@
 The ''XcDESKeyParity'' function turns a key into a DES key which requires odd-parity per byte.
-=== Pseudocode ===
+{{FIXME|reason=Mention crypto vector}}
-{{FIXME|reason=This should be removed from here, and instead we should just link to an actual implementation of the algorithm}}
+=== Links ===
-<pre>
+* [https://github.com/Cxbx-Reloaded/Cxbx-Reloaded/blob/f73114df61d943ba73b329a6e4bd6805254af243/src/CxbxKrnl/EmuKrnlXc.cpp#L234 XcDESKeyParity implementation in Cxbx-Reloaded]

← Older revision		Revision as of 23:58, 2 October 2018
Line 1:		Line 1:
		+	The ''XcDESKeyParity'' function turns a key into a DES key which requires odd-parity per byte.
		+
	=== Pseudocode ===		=== Pseudocode ===
		+
		+	{{FIXME\|reason=This should be removed from here, and instead we should just link to an actual implementation of the algorithm}}

	<pre>		<pre>