Use const List<int> where possible to prevent accidental mutation.

Author: elliotwutingfeng

lib/src/core/kiasu_bc.dart

@@ -10,7 +10,7 @@ const int gfModulus = 0x1b; // Irreducible polynomial: x^8 + x^4 + x^3 + x + 1.
 const int gfHighBit = 0x80; // Used for carry detection in GF multiplication.
 
 /// AES S-box.
-final List<int> sbox = [
+const List<int> sbox = [
   0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b,
   //
   0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
@@ -57,7 +57,7 @@ final List<int> sbox = [
 ];
 
 /// AES inverse S-box.
-final List<int> invSbox = [
+const List<int> invSbox = [
   0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e,
   //
   0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
@@ -104,7 +104,7 @@ final List<int> invSbox = [
 ];
 
 /// AES round constants.
-final List<int> rcon = [
+const List<int> rcon = [
   0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36,
   //
 ];