diff --git a/aes.c b/aes.c
index 18e3f38..776259c 100644
--- a/aes.c
+++ b/aes.c
@@ -240,7 +240,7 @@ void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv)
 
 // This function adds the round key to state.
 // The round key is added to the state by an XOR function.
-static void AddRoundKey(uint8_t round,state_t* state,uint8_t* RoundKey)
+static void AddRoundKey(uint8_t round, state_t* state, const uint8_t* RoundKey)
 {
   uint8_t i,j;
   for (i = 0; i < 4; ++i)
@@ -408,7 +408,7 @@ static void InvShiftRows(state_t* state)
 #endif // #if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
 
 // Cipher is the main function that encrypts the PlainText.
-static void Cipher(state_t* state, uint8_t* RoundKey)
+static void Cipher(state_t* state, const uint8_t* RoundKey)
 {
   uint8_t round = 0;
 
@@ -434,7 +434,7 @@ static void Cipher(state_t* state, uint8_t* RoundKey)
 }
 
 #if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
-static void InvCipher(state_t* state,uint8_t* RoundKey)
+static void InvCipher(state_t* state, const uint8_t* RoundKey)
 {
   uint8_t round = 0;
 
@@ -466,13 +466,13 @@ static void InvCipher(state_t* state,uint8_t* RoundKey)
 #if defined(ECB) && (ECB == 1)
 
 
-void AES_ECB_encrypt(struct AES_ctx *ctx, uint8_t* buf)
+void AES_ECB_encrypt(const struct AES_ctx *ctx, uint8_t* buf)
 {
   // The next function call encrypts the PlainText with the Key using AES algorithm.
   Cipher((state_t*)buf, ctx->RoundKey);
 }
 
-void AES_ECB_decrypt(struct AES_ctx* ctx, uint8_t* buf)
+void AES_ECB_decrypt(const struct AES_ctx* ctx, uint8_t* buf)
 {
   // The next function call decrypts the PlainText with the Key using AES algorithm.
   InvCipher((state_t*)buf, ctx->RoundKey);
@@ -488,7 +488,7 @@ void AES_ECB_decrypt(struct AES_ctx* ctx, uint8_t* buf)
 #if defined(CBC) && (CBC == 1)
 
 
-static void XorWithIv(uint8_t* buf, uint8_t* Iv)
+static void XorWithIv(uint8_t* buf, const uint8_t* Iv)
 {
   uint8_t i;
   for (i = 0; i < AES_BLOCKLEN; ++i) // The block in AES is always 128bit no matter the key size
@@ -497,7 +497,7 @@ static void XorWithIv(uint8_t* buf, uint8_t* Iv)
   }
 }
 
-void AES_CBC_encrypt_buffer(struct AES_ctx *ctx,uint8_t* buf, uint32_t length)
+void AES_CBC_encrypt_buffer(struct AES_ctx *ctx, uint8_t* buf, uint32_t length)
 {
   uintptr_t i;
   uint8_t *Iv = ctx->Iv;
@@ -552,9 +552,9 @@ void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length)
       /* Increment Iv and handle overflow */
       for (bi = (AES_BLOCKLEN - 1); bi >= 0; --bi)
       {
-	/* inc will owerflow */
+	    /* inc will overflow */
         if (ctx->Iv[bi] == 255)
-	{
+	    {
           ctx->Iv[bi] = 0;
           continue;
         } 
diff --git a/aes.h b/aes.h
index 1daab47..87f1471 100644
--- a/aes.h
+++ b/aes.h
@@ -58,8 +58,8 @@ void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv);
 // 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(struct AES_ctx* ctx, uint8_t* buf);
-void AES_ECB_decrypt(struct AES_ctx* ctx, uint8_t* buf);
+void AES_ECB_encrypt(const struct AES_ctx* ctx, uint8_t* buf);
+void AES_ECB_decrypt(const struct AES_ctx* ctx, uint8_t* buf);
 
 #endif // #if defined(ECB) && (ECB == !)