diff --git a/include/mbedtls/chacha20.h b/include/mbedtls/chacha20.h
new file mode 100644
index 0000000..ab10a96
--- /dev/null
+++ b/include/mbedtls/chacha20.h
@@ -0,0 +1,169 @@
+/**
+ * \file chacha20.h
+ *
+ * \brief ChaCha20 cipher.
+ *
+ * \author Daniel King <damaki.gh@gmail.com>
+ *
+ *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+#ifndef MBEDTLS_CHACHA20_H
+#define MBEDTLS_CHACHA20_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if !defined(MBEDTLS_CHACHA20_ALT)
+
+#include <stdint.h>
+#include <stddef.h>
+
+#define MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA -0x003B /**< Invalid input parameter(s). */
+
+typedef struct
+{
+    uint32_t initial_state[16];  /*! Holds the initial state (before round operations) */
+    uint32_t working_state[16];  /*! Holds the working state (after round operations) */
+    uint8_t  keystream8[64];     /*! Holds leftover keystream bytes */
+    size_t keystream_bytes_used; /*! Number of keystream bytes currently used */
+}
+mbedtls_chacha20_context;
+
+/**
+ * \brief           Initialize ChaCha20 context
+ *
+ * \param ctx       ChaCha20 context to be initialized
+ */
+void mbedtls_chacha20_init( mbedtls_chacha20_context *ctx );
+
+/**
+ * \brief           Clear ChaCha20 context
+ *
+ * \param ctx       ChaCha20 context to be cleared
+ */
+void mbedtls_chacha20_free( mbedtls_chacha20_context *ctx );
+
+/**
+ * \brief           Set the ChaCha20 key.
+ *
+ * \note            The nonce and counter must be set after calling this function,
+ *                  before data can be encrypted/decrypted. The nonce and
+ *                  counter are set by calling mbedtls_chacha20_starts.
+ *
+ * \see             mbedtls_chacha20_starts
+ *
+ * \param ctx       The context to setup.
+ * \param key       Buffer containing the 256-bit key. Must be 32 bytes in length.
+ *
+ * \return          MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA is returned if ctx or key
+ *                  is NULL, or if key_bits is not 128 or 256.
+ *                  Otherwise, 0 is returned to indicate success.
+ */
+int mbedtls_chacha20_setkey( mbedtls_chacha20_context *ctx,
+                             const unsigned char key[32] );
+
+/**
+ * \brief           Set the ChaCha20 nonce and initial counter value.
+ *
+ * \note            A ChaCha20 context can be re-used with the same key by
+ *                  calling this function to change the nonce and/or initial
+ *                  counter value.
+ *
+ * \param ctx       The ChaCha20 context.
+ * \param nonce     Buffer containing the 96-bit nonce. Must be 12 bytes in size.
+ * \param counter   Initial counter value to use. This is usually 0.
+ *
+ * \return          MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA is returned if ctx or
+ *                  nonce is NULL.
+ *                  Otherwise, 0 is returned to indicate success.
+ */
+int mbedtls_chacha20_starts( mbedtls_chacha20_context* ctx,
+                             const unsigned char nonce[12],
+                             uint32_t counter );
+
+/**
+ * \brief           Encrypt or decrypt data.
+ *
+ *                  This function is used to both encrypt and decrypt data.
+ *
+ * \note            The \p input and \p output buffers may overlap, but only
+ *                  if input >= output (i.e. only if input points ahead of
+ *                  the output pointer).
+ *
+ * \note            mbedtls_chacha20_setkey and mbedtls_chacha20_starts must be
+ *                  called at least once to setup the context before this function
+ *                  can be called.
+ *
+ * \param ctx       The ChaCha20 context.
+ * \param size      The length (in bytes) to process. This can have any length.
+ * \param input     Buffer containing the input data.
+ * \param output    Buffer containing the output data.
+ *
+ * \return          MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if the ctx, input, or
+ *                  output pointers are NULL.
+ *                  Otherwise, 0 is returned to indicate success.
+ */
+int mbedtls_chacha20_process( mbedtls_chacha20_context *ctx,
+                              size_t size,
+                              const unsigned char *input,
+                              unsigned char *output );
+
+#else  /* MBEDTLS_CHACHA20_ALT */
+#include "chacha20_alt.h"
+#endif /* MBEDTLS_CHACHA20_ALT */
+
+/**
+ * \brief           Encrypt or decrypt a message using ChaCha20.
+ *
+ *                  This function is used the same way for encrypting and
+ *                  decrypting data. It's not necessary to specify which
+ *                  operation is being performed.
+ *
+ * \note            The \p input and \p output buffers may overlap, but only
+ *                  if input >= output (i.e. only if input points ahead of
+ *                  the output pointer).
+ *
+ * \param key       Buffer containing the 256-bit key. Must be 32 bytes in length.
+ * \param nonce     Buffer containing the 96-bit nonce. Must be 12 bytes in length.
+ * \param counter   The initial counter value. This is usually 0.
+ * \param data_len  The number of bytes to process.
+ * \param input     Buffer containing the input data (data to encrypt or decrypt).
+ * \param output    Buffer to where the processed data is written.
+ *
+ * \return          MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if key, nonce, input,
+ *                  or output is NULL.
+ *                  Otherwise, 0 is returned to indicate success.
+ */
+int mbedtls_chacha20_crypt( const unsigned char key[32],
+                            const unsigned char nonce[12],
+                            uint32_t counter,
+                            size_t data_len,
+                            const unsigned char* input,
+                            unsigned char* output );
+
+/**
+ * \brief           Checkup routine
+ *
+ * \return          0 if successful, or 1 if the test failed
+ */
+int mbedtls_chacha20_self_test( int verbose );
+
+#endif /* MBEDTLS_CHACHA20_H */