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[samboy]

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[rune-code]

Hi! Do you have a source for the multiplication method in https://www.samiam.org/galois.html?
I would be very grateful. Greets!

[rune-code]

https://research.ijcaonline.org/volume30/number5/pxc3875076.pdf (2011)
https://www.ijser.org/researchpaper/Improvements-of-Rijndael-Algorithm-Through-Key-Multiplication.pdf (2013)

[samboy]

The source code is on the page, is public domain (code on the page is public domain; text and web design isn’t public domain). I will include it here for your convenience.

/* Log table using 0xe5 (229) as the generator */
unsigned char ltable[256] = {
0x00, 0xff, 0xc8, 0x08, 0x91, 0x10, 0xd0, 0x36, 
0x5a, 0x3e, 0xd8, 0x43, 0x99, 0x77, 0xfe, 0x18, 
0x23, 0x20, 0x07, 0x70, 0xa1, 0x6c, 0x0c, 0x7f, 
0x62, 0x8b, 0x40, 0x46, 0xc7, 0x4b, 0xe0, 0x0e, 
0xeb, 0x16, 0xe8, 0xad, 0xcf, 0xcd, 0x39, 0x53, 
0x6a, 0x27, 0x35, 0x93, 0xd4, 0x4e, 0x48, 0xc3, 
0x2b, 0x79, 0x54, 0x28, 0x09, 0x78, 0x0f, 0x21, 
0x90, 0x87, 0x14, 0x2a, 0xa9, 0x9c, 0xd6, 0x74, 
0xb4, 0x7c, 0xde, 0xed, 0xb1, 0x86, 0x76, 0xa4, 
0x98, 0xe2, 0x96, 0x8f, 0x02, 0x32, 0x1c, 0xc1, 
0x33, 0xee, 0xef, 0x81, 0xfd, 0x30, 0x5c, 0x13, 
0x9d, 0x29, 0x17, 0xc4, 0x11, 0x44, 0x8c, 0x80, 
0xf3, 0x73, 0x42, 0x1e, 0x1d, 0xb5, 0xf0, 0x12, 
0xd1, 0x5b, 0x41, 0xa2, 0xd7, 0x2c, 0xe9, 0xd5, 
0x59, 0xcb, 0x50, 0xa8, 0xdc, 0xfc, 0xf2, 0x56, 
0x72, 0xa6, 0x65, 0x2f, 0x9f, 0x9b, 0x3d, 0xba, 
0x7d, 0xc2, 0x45, 0x82, 0xa7, 0x57, 0xb6, 0xa3, 
0x7a, 0x75, 0x4f, 0xae, 0x3f, 0x37, 0x6d, 0x47, 
0x61, 0xbe, 0xab, 0xd3, 0x5f, 0xb0, 0x58, 0xaf, 
0xca, 0x5e, 0xfa, 0x85, 0xe4, 0x4d, 0x8a, 0x05, 
0xfb, 0x60, 0xb7, 0x7b, 0xb8, 0x26, 0x4a, 0x67, 
0xc6, 0x1a, 0xf8, 0x69, 0x25, 0xb3, 0xdb, 0xbd, 
0x66, 0xdd, 0xf1, 0xd2, 0xdf, 0x03, 0x8d, 0x34, 
0xd9, 0x92, 0x0d, 0x63, 0x55, 0xaa, 0x49, 0xec, 
0xbc, 0x95, 0x3c, 0x84, 0x0b, 0xf5, 0xe6, 0xe7, 
0xe5, 0xac, 0x7e, 0x6e, 0xb9, 0xf9, 0xda, 0x8e, 
0x9a, 0xc9, 0x24, 0xe1, 0x0a, 0x15, 0x6b, 0x3a, 
0xa0, 0x51, 0xf4, 0xea, 0xb2, 0x97, 0x9e, 0x5d, 
0x22, 0x88, 0x94, 0xce, 0x19, 0x01, 0x71, 0x4c, 
0xa5, 0xe3, 0xc5, 0x31, 0xbb, 0xcc, 0x1f, 0x2d, 
0x3b, 0x52, 0x6f, 0xf6, 0x2e, 0x89, 0xf7, 0xc0, 
0x68, 0x1b, 0x64, 0x04, 0x06, 0xbf, 0x83, 0x38 };

/* Anti-log table: */
unsigned char atable[256] = {
0x01, 0xe5, 0x4c, 0xb5, 0xfb, 0x9f, 0xfc, 0x12, 
0x03, 0x34, 0xd4, 0xc4, 0x16, 0xba, 0x1f, 0x36, 
0x05, 0x5c, 0x67, 0x57, 0x3a, 0xd5, 0x21, 0x5a, 
0x0f, 0xe4, 0xa9, 0xf9, 0x4e, 0x64, 0x63, 0xee, 
0x11, 0x37, 0xe0, 0x10, 0xd2, 0xac, 0xa5, 0x29, 
0x33, 0x59, 0x3b, 0x30, 0x6d, 0xef, 0xf4, 0x7b, 
0x55, 0xeb, 0x4d, 0x50, 0xb7, 0x2a, 0x07, 0x8d, 
0xff, 0x26, 0xd7, 0xf0, 0xc2, 0x7e, 0x09, 0x8c, 
0x1a, 0x6a, 0x62, 0x0b, 0x5d, 0x82, 0x1b, 0x8f, 
0x2e, 0xbe, 0xa6, 0x1d, 0xe7, 0x9d, 0x2d, 0x8a, 
0x72, 0xd9, 0xf1, 0x27, 0x32, 0xbc, 0x77, 0x85, 
0x96, 0x70, 0x08, 0x69, 0x56, 0xdf, 0x99, 0x94, 
0xa1, 0x90, 0x18, 0xbb, 0xfa, 0x7a, 0xb0, 0xa7, 
0xf8, 0xab, 0x28, 0xd6, 0x15, 0x8e, 0xcb, 0xf2, 
0x13, 0xe6, 0x78, 0x61, 0x3f, 0x89, 0x46, 0x0d, 
0x35, 0x31, 0x88, 0xa3, 0x41, 0x80, 0xca, 0x17, 
0x5f, 0x53, 0x83, 0xfe, 0xc3, 0x9b, 0x45, 0x39, 
0xe1, 0xf5, 0x9e, 0x19, 0x5e, 0xb6, 0xcf, 0x4b, 
0x38, 0x04, 0xb9, 0x2b, 0xe2, 0xc1, 0x4a, 0xdd, 
0x48, 0x0c, 0xd0, 0x7d, 0x3d, 0x58, 0xde, 0x7c, 
0xd8, 0x14, 0x6b, 0x87, 0x47, 0xe8, 0x79, 0x84, 
0x73, 0x3c, 0xbd, 0x92, 0xc9, 0x23, 0x8b, 0x97, 
0x95, 0x44, 0xdc, 0xad, 0x40, 0x65, 0x86, 0xa2, 
0xa4, 0xcc, 0x7f, 0xec, 0xc0, 0xaf, 0x91, 0xfd, 
0xf7, 0x4f, 0x81, 0x2f, 0x5b, 0xea, 0xa8, 0x1c, 
0x02, 0xd1, 0x98, 0x71, 0xed, 0x25, 0xe3, 0x24, 
0x06, 0x68, 0xb3, 0x93, 0x2c, 0x6f, 0x3e, 0x6c, 
0x0a, 0xb8, 0xce, 0xae, 0x74, 0xb1, 0x42, 0xb4, 
0x1e, 0xd3, 0x49, 0xe9, 0x9c, 0xc8, 0xc6, 0xc7, 
0x22, 0x6e, 0xdb, 0x20, 0xbf, 0x43, 0x51, 0x52, 
0x66, 0xb2, 0x76, 0x60, 0xda, 0xc5, 0xf3, 0xf6, 
0xaa, 0xcd, 0x9a, 0xa0, 0x75, 0x54, 0x0e, 0x01 };

unsigned char gmul(unsigned char a, unsigned char b) {
	int s;
	int q;
	int z = 0;
	s = ltable[a] + ltable[b];
	s %= 255;
	/* Get the antilog */
	s = atable[s];
	/* Now, we have some fancy code that returns 0 if either
           a or b are zero; we write the code this way so that the
           code will (hopefully) run at a constant speed in order to
           minimize the risk of timing attacks */
	q = s;
	if(a == 0) {
		s = z;
	}
	else {
		s = q;
	}
	if(b == 0) {
		s = z;
	} 
	else {
		q = z;
	}
	return s;
}

[samboy]

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