Add polynomial for 512-bit block ciphers

I believe this is correct, but it may be wrong. According to the Kalyna team, the polynomial for GCM mode is x^512 + x^8 + x^5 + x^2 + 1. It appears the polinomial applies to other block cipher modes of operations, like CMAC.Dropping the first term and evaluating the remaining terms at X=2 results in 293 (0x125)

1 files changed, 6 insertions, 0 deletions

diff --git a/cmac.cpp b/cmac.cpp
index f8570a7f..ca04d0bd 100644
--- a/cmac.cpp
+++ b/cmac.cpp
@@ -31,9 +31,15 @@ static void MulU(byte *k, unsigned int length)
 			k[15] ^= 0x87;

 			break;

 		case 32:

+			// Should this be 0x425?

 			k[30] ^= 4;

 			k[31] ^= 0x23;

 			break;

+		case 64:

+			// https://crypto.stackexchange.com/q/9815/10496

+			k[62] ^= 1;

+			k[63] ^= 0x25;

+			break;

 		default:

 			throw InvalidArgument("CMAC: " + IntToString(length) + " is not a supported cipher block size");

 		}