diff --git a/aes.c b/aes.c
index f0fc791..4481f7b 100644
--- a/aes.c
+++ b/aes.c
@@ -498,9 +498,9 @@ static void XorWithIv(uint8_t* buf, const 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, size_t length)
 {
-  uintptr_t i;
+  size_t i;
   uint8_t *Iv = ctx->Iv;
   for (i = 0; i < length; i += AES_BLOCKLEN)
   {
@@ -513,9 +513,9 @@ void AES_CBC_encrypt_buffer(struct AES_ctx *ctx, uint8_t* buf, uint32_t length)
   memcpy(ctx->Iv, Iv, AES_BLOCKLEN);
 }
 
-void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf,  uint32_t length)
+void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length)
 {
-  uintptr_t i;
+  size_t i;
   uint8_t storeNextIv[AES_BLOCKLEN];
   for (i = 0; i < length; i += AES_BLOCKLEN)
   {
@@ -535,11 +535,11 @@ void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf,  uint32_t length)
 #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(struct AES_ctx* ctx, uint8_t* buf, uint32_t length)
+void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length)
 {
   uint8_t buffer[AES_BLOCKLEN];
   
-  unsigned i;
+  size_t i;
   int bi;
   for (i = 0, bi = AES_BLOCKLEN; i < length; ++i, ++bi)
   {
diff --git a/aes.h b/aes.h
index 0d3b2e0..ade29e8 100644
--- a/aes.h
+++ b/aes.h
@@ -69,8 +69,8 @@ void AES_ECB_decrypt(const struct AES_ctx* ctx, uint8_t* buf);
 // 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(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
-void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
+void AES_CBC_encrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
+void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
 
 #endif // #if defined(CBC) && (CBC == 1)
 
@@ -82,7 +82,7 @@ void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
 // 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(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
+void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
 
 #endif // #if defined(CTR) && (CTR == 1)