add encryption/decryption

1 files changed, 610 insertions, 0 deletions

diff --git a/lib/nes/app/crypto/aes256.cc b/lib/nes/app/crypto/aes256.cc
new file mode 100644
index 0000000..1fcaf9d
--- /dev/null
+++ b/lib/nes/app/crypto/aes256.cc
@@ -0,0 +1,610 @@
+#include "nes/app/crypto/aes256.hh"
+
+#include "nes/common/utils.hh"
+
+namespace nes::app
+{
+	// Implementation copied from: https://github.com/kokke/tiny-AES-c/tree/master
+
+	namespace
+	{
+#define CTR 1
+#define AES256 1
+#define AES_BLOCKLEN 16 // Block length in bytes - AES is 128b block only
+
+#if defined(AES256) && (AES256 == 1)
+#define AES_KEYLEN 32
+#define AES_keyExpSize 240
+#elif defined(AES192) && (AES192 == 1)
+#define AES_KEYLEN 24
+#define AES_keyExpSize 208
+#else
+#define AES_KEYLEN 16 // Key length in bytes
+#define AES_keyExpSize 176
+#endif
+
+		struct AES_ctx
+		{
+			u8 RoundKey[AES_keyExpSize];
+#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))
+			u8 Iv[AES_BLOCKLEN];
+#endif
+		};
+
+		void AES_init_ctx(AES_ctx* ctx, u8 const* key);
+
+#if defined(ECB) && (ECB == 1)
+		// buffer size is exactly AES_BLOCKLEN bytes;
+		// you need only AES_init_ctx as IV is not used in ECB
+		// NB: ECB is considered insecure for most uses
+		void AES_ECB_encrypt(const AES_ctx* ctx, u8* buf);
+		void AES_ECB_decrypt(const AES_ctx* ctx, u8* buf);
+#endif // #if defined(ECB) && (ECB == !)
+
+#if defined(CBC) && (CBC == 1)
+		// buffer size MUST be mutile of AES_BLOCKLEN;
+		// Suggest https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7 for padding scheme
+		// NOTES: you need to set IV in ctx via AES_init_ctx_iv() or AES_ctx_set_iv()
+		//        no IV should ever be reused with the same key
+		void AES_CBC_encrypt_buffer(AES_ctx* ctx, u8* buf, u32 length);
+		void AES_CBC_decrypt_buffer(AES_ctx* ctx, u8* buf, u32 length);
+#endif // #if defined(CBC) && (CBC == 1)
+
+#if defined(CTR) && (CTR == 1)
+		// Same function for encrypting as for decrypting.
+		// IV is incremented for every block, and used after encryption as XOR-compliment for output
+		// Suggesting https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7 for padding scheme
+		// NOTES: you need to set IV in ctx with AES_init_ctx_iv() or AES_ctx_set_iv()
+		//        no IV should ever be reused with the same key
+		void AES_CTR_xcrypt_buffer(AES_ctx* ctx, u8* buf, u32 length);
+#endif // #if defined(CTR) && (CTR == 1)
+
+/*
+
+This is an implementation of the AES algorithm, specifically ECB, CTR and CBC mode.
+Block size can be chosen in aes.h - available choices are AES128, AES192, AES256.
+
+The implementation is verified against the test vectors in:
+  National Institute of Standards and Technology Special Publication 800-38A 2001 ED
+
+ECB-AES128
+----------
+
+  plain-text:
+	6bc1bee22e409f96e93d7e117393172a
+	ae2d8a571e03ac9c9eb76fac45af8e51
+	30c81c46a35ce411e5fbc1191a0a52ef
+	f69f2445df4f9b17ad2b417be66c3710
+
+  key:
+	2b7e151628aed2a6abf7158809cf4f3c
+
+  resulting cipher
+	3ad77bb40d7a3660a89ecaf32466ef97
+	f5d3d58503b9699de785895a96fdbaaf
+	43b1cd7f598ece23881b00e3ed030688
+	7b0c785e27e8ad3f8223207104725dd4
+
+
+NOTE:   String length must be evenly divisible by 16byte (str_len % 16 == 0)
+		You should pad the end of the string with zeros if this is not the case.
+		For AES192/256 the key size is proportionally larger.
+
+*/
+
+/*****************************************************************************/
+/* Defines:                                                                  */
+/*****************************************************************************/
+// The number of columns comprising a state in AES. This is a constant in AES. Value=4
+#define Nb 4
+
+#if defined(AES256) && (AES256 == 1)
+#define Nk 8
+#define Nr 14
+#elif defined(AES192) && (AES192 == 1)
+#define Nk 6
+#define Nr 12
+#else
+#define Nk 4 // The number of 32 bit words in a key.
+#define Nr 10 // The number of rounds in AES Cipher.
+#endif
+
+// jcallan@github points out that declaring Multiply as a function
+// reduces code size considerably with the Keil ARM compiler.
+// See this link for more information: https://github.com/kokke/tiny-AES-C/pull/3
+#ifndef MULTIPLY_AS_A_FUNCTION
+#define MULTIPLY_AS_A_FUNCTION 0
+#endif
+
+		/*****************************************************************************/
+		/* Private variables:                                                        */
+		/*****************************************************************************/
+		// state - array holding the intermediate results during decryption.
+		using state_t = u8[4][4];
+
+		// The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
+		// The numbers below can be computed dynamically trading ROM for RAM -
+		// This can be useful in (embedded) bootloader applications, where ROM is often limited.
+		u8 const sbox[256] = {
+			// 0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F
+			0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82,
+			0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26,
+			0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96,
+			0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
+			0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb,
+			0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f,
+			0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff,
+			0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
+			0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32,
+			0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d,
+			0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6,
+			0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
+			0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e,
+			0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f,
+			0xb0, 0x54, 0xbb, 0x16
+		};
+
+#if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
+		const u8 rsbox[256] = {
+			0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3,
+			0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32,
+			0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9,
+			0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
+			0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15,
+			0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05,
+			0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13,
+			0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
+			0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1,
+			0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b,
+			0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07,
+			0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
+			0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb,
+			0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63,
+			0x55, 0x21, 0x0c, 0x7d
+		};
+#endif
+
+		// The round constant word array, Rcon[i], contains the values given by
+		// x to the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
+		u8 const Rcon[11] = { 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };
+
+/*
+ * Jordan Goulder points out in PR #12 (https://github.com/kokke/tiny-AES-C/pull/12),
+ * that you can remove most of the elements in the Rcon array, because they are unused.
+ *
+ * From Wikipedia's article on the Rijndael key schedule @ https://en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon
+ *
+ * "Only the first some of these constants are actually used – up to rcon[10] for AES-128 (as 11 round keys are needed),
+ *  up to rcon[8] for AES-192, up to rcon[7] for AES-256. rcon[0] is not used in AES algorithm."
+ */
+
+/*****************************************************************************/
+/* Private functions:                                                        */
+/*****************************************************************************/
+/*
+u8 getSBoxValue(u8 num)
+{
+  return sbox[num];
+}
+*/
+#define getSBoxValue(num) (sbox[(num)])
+
+		// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
+		void KeyExpansion(u8* RoundKey, u8 const* Key)
+		{
+			unsigned i, j, k;
+			u8 tempa[4]; // Used for the column/row operations
+
+			// The first round key is the key itself.
+			for (i = 0; i < Nk; ++i)
+			{
+				RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
+				RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
+				RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
+				RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
+			}
+
+			// All other round keys are found from the previous round keys.
+			for (i = Nk; i < Nb * (Nr + 1); ++i)
+			{
+				{
+					k = (i - 1) * 4;
+					tempa[0] = RoundKey[k + 0];
+					tempa[1] = RoundKey[k + 1];
+					tempa[2] = RoundKey[k + 2];
+					tempa[3] = RoundKey[k + 3];
+				}
+
+				if (i % Nk == 0)
+				{
+					// This function shifts the 4 bytes in a word to the left once.
+					// [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
+
+					// Function RotWord()
+					{
+						u8 const u8tmp = tempa[0];
+						tempa[0] = tempa[1];
+						tempa[1] = tempa[2];
+						tempa[2] = tempa[3];
+						tempa[3] = u8tmp;
+					}
+
+					// SubWord() is a function that takes a four-byte input word and
+					// applies the S-box to each of the four bytes to produce an output word.
+
+					// Function Subword()
+					{
+						tempa[0] = getSBoxValue(tempa[0]);
+						tempa[1] = getSBoxValue(tempa[1]);
+						tempa[2] = getSBoxValue(tempa[2]);
+						tempa[3] = getSBoxValue(tempa[3]);
+					}
+
+					tempa[0] = tempa[0] ^ Rcon[i / Nk];
+				}
+#if defined(AES256) && (AES256 == 1)
+				if (i % Nk == 4)
+				{
+					// Function Subword()
+					{
+						tempa[0] = getSBoxValue(tempa[0]);
+						tempa[1] = getSBoxValue(tempa[1]);
+						tempa[2] = getSBoxValue(tempa[2]);
+						tempa[3] = getSBoxValue(tempa[3]);
+					}
+				}
+#endif
+				j = i * 4;
+				k = (i - Nk) * 4;
+				RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
+				RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
+				RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
+				RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
+			}
+		}
+
+		void AES_init_ctx(AES_ctx* ctx, u8 const* key)
+		{
+			KeyExpansion(ctx->RoundKey, key);
+		}
+
+		// This function adds the round key to state.
+		// The round key is added to the state by an XOR function.
+		void AddRoundKey(u8 round, state_t* state, u8 const* RoundKey)
+		{
+			for (u8 i = 0; i < 4; ++i)
+			{
+				for (u8 j = 0; j < 4; ++j)
+				{
+					(*state)[i][j] ^= RoundKey[(round * Nb * 4) + (i * Nb) + j];
+				}
+			}
+		}
+
+		// The SubBytes Function Substitutes the values in the
+		// state matrix with values in an S-box.
+		void SubBytes(state_t* state)
+		{
+			for (u8 i = 0; i < 4; ++i)
+			{
+				for (u8 j = 0; j < 4; ++j)
+				{
+					(*state)[j][i] = getSBoxValue((*state)[j][i]);
+				}
+			}
+		}
+
+		// The ShiftRows() function shifts the rows in the state to the left.
+		// Each row is shifted with different offset.
+		// Offset = Row number. So the first row is not shifted.
+		void ShiftRows(state_t* state)
+		{
+			// Rotate first row 1 columns to left
+			u8 temp = (*state)[0][1];
+			(*state)[0][1] = (*state)[1][1];
+			(*state)[1][1] = (*state)[2][1];
+			(*state)[2][1] = (*state)[3][1];
+			(*state)[3][1] = temp;
+
+			// Rotate second row 2 columns to left
+			temp = (*state)[0][2];
+			(*state)[0][2] = (*state)[2][2];
+			(*state)[2][2] = temp;
+
+			temp = (*state)[1][2];
+			(*state)[1][2] = (*state)[3][2];
+			(*state)[3][2] = temp;
+
+			// Rotate third row 3 columns to left
+			temp = (*state)[0][3];
+			(*state)[0][3] = (*state)[3][3];
+			(*state)[3][3] = (*state)[2][3];
+			(*state)[2][3] = (*state)[1][3];
+			(*state)[1][3] = temp;
+		}
+
+		u8 xtime(u8 x)
+		{
+			return ((x << 1) ^ (((x >> 7) & 1) * 0x1b));
+		}
+
+		// MixColumns function mixes the columns of the state matrix
+		void MixColumns(state_t* state)
+		{
+			for (u8 i = 0; i < 4; ++i)
+			{
+				u8 t = (*state)[i][0];
+				u8 Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3];
+				u8 Tm = (*state)[i][0] ^ (*state)[i][1];
+				Tm = xtime(Tm);
+				(*state)[i][0] ^= Tm ^ Tmp;
+				Tm = (*state)[i][1] ^ (*state)[i][2];
+				Tm = xtime(Tm);
+				(*state)[i][1] ^= Tm ^ Tmp;
+				Tm = (*state)[i][2] ^ (*state)[i][3];
+				Tm = xtime(Tm);
+				(*state)[i][2] ^= Tm ^ Tmp;
+				Tm = (*state)[i][3] ^ t;
+				Tm = xtime(Tm);
+				(*state)[i][3] ^= Tm ^ Tmp;
+			}
+		}
+
+// Multiply is used to multiply numbers in the field GF(2^8)
+// Note: The last call to xtime() is unneeded, but often ends up generating a smaller binary
+//       The compiler seems to be able to vectorize the operation better this way.
+//       See https://github.com/kokke/tiny-AES-c/pull/34
+#if MULTIPLY_AS_A_FUNCTION
+		u8 Multiply(u8 x, u8 y)
+		{
+			return (
+				((y & 1) * x) ^ ((y >> 1 & 1) * xtime(x)) ^ ((y >> 2 & 1) * xtime(xtime(x))) ^
+				((y >> 3 & 1) * xtime(xtime(xtime(x)))) ^
+				((y >> 4 & 1) * xtime(xtime(xtime(xtime(x)))))); /* this last call to xtime() can be omitted */
+		}
+#else
+#define Multiply(x, y) \
+	(((y & 1) * x) ^ ((y >> 1 & 1) * xtime(x)) ^ ((y >> 2 & 1) * xtime(xtime(x))) ^ \
+	 ((y >> 3 & 1) * xtime(xtime(xtime(x)))) ^ ((y >> 4 & 1) * xtime(xtime(xtime(xtime(x))))))
+
+#endif
+
+#if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
+/*
+u8 getSBoxInvert(u8 num)
+{
+  return rsbox[num];
+}
+*/
+#define getSBoxInvert(num) (rsbox[(num)])
+
+		// MixColumns function mixes the columns of the state matrix.
+		// The method used to multiply may be difficult to understand for the inexperienced.
+		// Please use the references to gain more information.
+		void InvMixColumns(state_t* state)
+		{
+			int i;
+			u8 a, b, c, d;
+			for (i = 0; i < 4; ++i)
+			{
+				a = (*state)[i][0];
+				b = (*state)[i][1];
+				c = (*state)[i][2];
+				d = (*state)[i][3];
+
+				(*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
+				(*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
+				(*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
+				(*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
+			}
+		}
+
+		// The SubBytes Function Substitutes the values in the
+		// state matrix with values in an S-box.
+		void InvSubBytes(state_t* state)
+		{
+			u8 i, j;
+			for (i = 0; i < 4; ++i)
+			{
+				for (j = 0; j < 4; ++j)
+				{
+					(*state)[j][i] = getSBoxInvert((*state)[j][i]);
+				}
+			}
+		}
+
+		void InvShiftRows(state_t* state)
+		{
+			u8 temp;
+
+			// Rotate first row 1 columns to right
+			temp = (*state)[3][1];
+			(*state)[3][1] = (*state)[2][1];
+			(*state)[2][1] = (*state)[1][1];
+			(*state)[1][1] = (*state)[0][1];
+			(*state)[0][1] = temp;
+
+			// Rotate second row 2 columns to right
+			temp = (*state)[0][2];
+			(*state)[0][2] = (*state)[2][2];
+			(*state)[2][2] = temp;
+
+			temp = (*state)[1][2];
+			(*state)[1][2] = (*state)[3][2];
+			(*state)[3][2] = temp;
+
+			// Rotate third row 3 columns to right
+			temp = (*state)[0][3];
+			(*state)[0][3] = (*state)[1][3];
+			(*state)[1][3] = (*state)[2][3];
+			(*state)[2][3] = (*state)[3][3];
+			(*state)[3][3] = temp;
+		}
+#endif // #if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
+
+		// Cipher is the main function that encrypts the PlainText.
+		void Cipher(state_t* state, u8 const* RoundKey)
+		{
+			u8 round = 0;
+
+			// Add the First round key to the state before starting the rounds.
+			AddRoundKey(0, state, RoundKey);
+
+			// There will be Nr rounds.
+			// The first Nr-1 rounds are identical.
+			// These Nr rounds are executed in the loop below.
+			// Last one without MixColumns()
+			for (round = 1;; ++round)
+			{
+				SubBytes(state);
+				ShiftRows(state);
+				if (round == Nr)
+				{
+					break;
+				}
+				MixColumns(state);
+				AddRoundKey(round, state, RoundKey);
+			}
+			// Add round key to last round
+			AddRoundKey(Nr, state, RoundKey);
+		}
+
+#if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
+		void InvCipher(state_t* state, const u8* RoundKey)
+		{
+			u8 round = 0;
+
+			// Add the First round key to the state before starting the rounds.
+			AddRoundKey(Nr, state, RoundKey);
+
+			// There will be Nr rounds.
+			// The first Nr-1 rounds are identical.
+			// These Nr rounds are executed in the loop below.
+			// Last one without InvMixColumn()
+			for (round = (Nr - 1);; --round)
+			{
+				InvShiftRows(state);
+				InvSubBytes(state);
+				AddRoundKey(round, state, RoundKey);
+				if (round == 0)
+				{
+					break;
+				}
+				InvMixColumns(state);
+			}
+		}
+#endif // #if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
+
+/*****************************************************************************/
+/* Public functions:                                                         */
+/*****************************************************************************/
+#if defined(ECB) && (ECB == 1)
+
+		void AES_ECB_encrypt(const AES_ctx* ctx, u8* buf)
+		{
+			// The next function call encrypts the PlainText with the Key using AES algorithm.
+			Cipher((state_t*)buf, ctx->RoundKey);
+		}
+
+		void AES_ECB_decrypt(const AES_ctx* ctx, u8* buf)
+		{
+			// The next function call decrypts the PlainText with the Key using AES algorithm.
+			InvCipher((state_t*)buf, ctx->RoundKey);
+		}
+
+#endif // #if defined(ECB) && (ECB == 1)
+
+#if defined(CBC) && (CBC == 1)
+
+		void XorWithIv(u8* buf, const u8* Iv)
+		{
+			u8 i;
+			for (i = 0; i < AES_BLOCKLEN; ++i) // The block in AES is always 128bit no matter the key size
+			{
+				buf[i] ^= Iv[i];
+			}
+		}
+
+		void AES_CBC_encrypt_buffer(AES_ctx* ctx, u8* buf, u32 length)
+		{
+			u32 i;
+			u8* Iv = ctx->Iv;
+			for (i = 0; i < length; i += AES_BLOCKLEN)
+			{
+				XorWithIv(buf, Iv);
+				Cipher((state_t*)buf, ctx->RoundKey);
+				Iv = buf;
+				buf += AES_BLOCKLEN;
+			}
+			/* store Iv in ctx for next call */
+			copy(Iv, ctx->Iv, AES_BLOCKLEN);
+		}
+
+		void AES_CBC_decrypt_buffer(AES_ctx* ctx, u8* buf, u32 length)
+		{
+			u32 i;
+			u8 storeNextIv[AES_BLOCKLEN];
+			for (i = 0; i < length; i += AES_BLOCKLEN)
+			{
+				copy(buf, storeNextIv, AES_BLOCKLEN);
+				InvCipher((state_t*)buf, ctx->RoundKey);
+				XorWithIv(buf, ctx->Iv);
+				copy(storeNextIv, ctx->Iv, AES_BLOCKLEN);
+				buf += AES_BLOCKLEN;
+			}
+		}
+
+#endif // #if defined(CBC) && (CBC == 1)
+
+#if defined(CTR) && (CTR == 1)
+
+		/* Symmetrical operation: same function for encrypting as for decrypting. Note any IV/nonce should never be
+		 * reused with the same key */
+		void AES_CTR_xcrypt_buffer(AES_ctx* ctx, u8* buf, u32 length)
+		{
+			u8 buffer[AES_BLOCKLEN];
+
+			u32 i;
+			int bi;
+			for (i = 0, bi = AES_BLOCKLEN; i < length; ++i, ++bi)
+			{
+				if (bi == AES_BLOCKLEN) /* we need to regen xor compliment in buffer */
+				{
+					copy(ctx->Iv, buffer, AES_BLOCKLEN);
+					Cipher(reinterpret_cast<state_t*>(buffer), ctx->RoundKey);
+
+					/* Increment Iv and handle overflow */
+					for (bi = (AES_BLOCKLEN - 1); bi >= 0; --bi)
+					{
+						/* inc will overflow */
+						if (ctx->Iv[bi] == 255)
+						{
+							ctx->Iv[bi] = 0;
+							continue;
+						}
+						ctx->Iv[bi] += 1;
+						break;
+					}
+					bi = 0;
+				}
+
+				buf[i] = (buf[i] ^ buffer[bi]);
+			}
+		}
+
+#endif // #if defined(CTR) && (CTR == 1)
+	} // namespace
+
+	auto aes256::encrypt(span<u8> const buffer, key const key) -> void
+	{
+		auto ctx = AES_ctx{};
+		AES_init_ctx(&ctx, key.get_data());
+		AES_CTR_xcrypt_buffer(&ctx, buffer.get_data(), buffer.get_length());
+	}
+
+	auto aes256::decrypt(span<u8> const buffer, key const key) -> void
+	{
+		// For CTR: Encryption is same as decryption.
+		return encrypt(buffer, key);
+	}
+} // namespace nes::app
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