diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index 251b6c6..b8f663d 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -3,6 +3,7 @@
 option(LINK_WITH_PTHREAD "Explicitly link mbed TLS library to pthread." OFF)
 
 set(src_crypto
+    aead_chacha20_poly1305.c
     aes.c
     aesni.c
     arc4.c
diff --git a/library/Makefile b/library/Makefile
index 5fd693b..de4bd5c 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -47,7 +47,8 @@
 DLEXT=dll
 endif
 
-OBJS_CRYPTO=	aes.o		aesni.o		arc4.o		\
+OBJS_CRYPTO=	aead_chacha20_poly1305.o	\
+		aes.o		aesni.o		arc4.o		\
 		asn1parse.o	asn1write.o	base64.o	\
 		bignum.o	blowfish.o	camellia.o	\
 		ccm.o		chacha20.o			\
diff --git a/library/aead_chacha20_poly1305.c b/library/aead_chacha20_poly1305.c
new file mode 100644
index 0000000..ab29dfa
--- /dev/null
+++ b/library/aead_chacha20_poly1305.c
@@ -0,0 +1,463 @@
+/**
+ * \file aead_chacha20_poly1305.c
+ *
+ * \brief ChaCha20-Poly1305 AEAD construction based on RFC 7539.
+ *
+ *  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)
+ */
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_AEAD_CHACHA20_POLY1305_C)
+
+#include "mbedtls/aead_chacha20_poly1305.h"
+#include <string.h>
+
+#if defined(MBEDTLS_SELF_TEST)
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdio.h>
+#define mbedtls_printf printf
+#endif /* MBEDTLS_PLATFORM_C */
+#endif /* MBEDTLS_SELF_TEST */
+
+#if !defined(MBEDTLS_AEAD_CHACHA20_POLY1305_ALT)
+
+#define AEAD_CHACHA20_POLY1305_STATE_INIT       ( 0 )
+#define AEAD_CHACHA20_POLY1305_STATE_AAD        ( 1 )
+#define AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT ( 2 ) /* Encrypting or decrypting */
+#define AEAD_CHACHA20_POLY1305_STATE_FINISHED   ( 3 )
+
+/* Implementation that should never be optimized out by the compiler */
+static void mbedtls_zeroize( void *v, size_t n ) {
+    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
+/**
+ * \brief           Adds padding bytes (zeroes) to pad the AAD for Poly1305.
+ *
+ * \param ctx       The ChaCha20-Poly1305 context.
+ */
+static void mbedtls_aead_chacha20_poly1305_pad_aad( mbedtls_aead_chacha20_poly1305_context *ctx )
+{
+    uint32_t partial_block_len = (uint32_t)( ctx->aad_len % 16U );
+    unsigned char zeroes[15];
+
+    if ( partial_block_len > 0U )
+    {
+        memset( zeroes, 0, sizeof(zeroes) );
+        (void)mbedtls_poly1305_update( &ctx->poly1305_ctx,
+                                       16U - partial_block_len,
+                                       zeroes );
+    }
+}
+
+/**
+ * \brief           Adds padding bytes (zeroes) to pad the ciphertext for Poly1305.
+ *
+ * \param ctx       The ChaCha20-Poly1305 context.
+ */
+static void mbedtls_aead_chacha20_poly1305_pad_ciphertext( mbedtls_aead_chacha20_poly1305_context *ctx )
+{
+    uint32_t partial_block_len = (uint32_t)( ctx->ciphertext_len % 16U );
+    unsigned char zeroes[15];
+
+    if ( partial_block_len > 0U )
+    {
+        memset( zeroes, 0, sizeof(zeroes) );
+        (void)mbedtls_poly1305_update( &ctx->poly1305_ctx,
+                                       16U - partial_block_len,
+                                       zeroes );
+    }
+}
+
+void mbedtls_aead_chacha20_poly1305_init( mbedtls_aead_chacha20_poly1305_context *ctx )
+{
+    if ( ctx != NULL )
+    {
+        mbedtls_chacha20_init( &ctx->chacha20_ctx );
+        mbedtls_poly1305_init( &ctx->poly1305_ctx );
+        ctx->aad_len        = 0U;
+        ctx->ciphertext_len = 0U;
+        ctx->state          = AEAD_CHACHA20_POLY1305_STATE_INIT;
+        ctx->mode           = MBEDTLS_AEAD_CHACHA20_POLY1305_ENCRYPT;
+    }
+}
+
+void mbedtls_aead_chacha20_poly1305_free( mbedtls_aead_chacha20_poly1305_context *ctx )
+{
+    if ( ctx != NULL )
+    {
+        mbedtls_chacha20_free( &ctx->chacha20_ctx );
+        mbedtls_poly1305_free( &ctx->poly1305_ctx );
+        ctx->aad_len        = 0U;
+        ctx->ciphertext_len = 0U;
+        ctx->state          = AEAD_CHACHA20_POLY1305_STATE_INIT;
+        ctx->mode           = MBEDTLS_AEAD_CHACHA20_POLY1305_ENCRYPT;
+    }
+}
+
+int mbedtls_aead_chacha20_poly1305_setkey( mbedtls_aead_chacha20_poly1305_context *ctx,
+                                           const unsigned char key[32] )
+{
+    int result;
+
+    if ( ( ctx == NULL ) || ( key == NULL ) )
+    {
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+    }
+
+    result = mbedtls_chacha20_setkey( &ctx->chacha20_ctx, key );
+
+    return( result );
+}
+
+int mbedtls_aead_chacha20_poly1305_starts( mbedtls_aead_chacha20_poly1305_context *ctx,
+                                           const unsigned char nonce[12],
+                                           mbedtls_aead_chacha20_poly1305_mode_t mode  )
+{
+    int result;
+    unsigned char poly1305_key[64];
+
+    if ( ( ctx == NULL ) || ( nonce == NULL ) )
+    {
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+    }
+
+    result = mbedtls_chacha20_starts( &ctx->chacha20_ctx, nonce, 1U );
+    if ( result != 0 )
+        goto cleanup;
+
+    /* Generate the Poly1305 key by getting the ChaCha20 keystream output with counter = 0.
+     * Only the first 256-bits (32 bytes) of the key is used for Poly1305.
+     * The other 256 bits are discarded.
+     */
+    result = mbedtls_chacha20_keystream_block( &ctx->chacha20_ctx, 0U, poly1305_key );
+    if ( result != 0 )
+        goto cleanup;
+
+    result = mbedtls_poly1305_setkey( &ctx->poly1305_ctx, poly1305_key );
+
+    if ( result == 0 )
+    {
+        ctx->aad_len        = 0U;
+        ctx->ciphertext_len = 0U;
+        ctx->state          = AEAD_CHACHA20_POLY1305_STATE_AAD;
+        ctx->mode           = mode;
+    }
+
+cleanup:
+    mbedtls_zeroize( poly1305_key, 64U );
+    return( result );
+}
+
+int mbedtls_aead_chacha20_poly1305_update_aad( mbedtls_aead_chacha20_poly1305_context *ctx,
+                                               size_t aad_len,
+                                               const unsigned char *aad )
+{
+    if ( ( ctx == NULL ) || ( aad == NULL ) )
+    {
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+    }
+    else if ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_AAD )
+    {
+        return (MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_STATE );
+    }
+
+    ctx->aad_len += aad_len;
+
+    return ( mbedtls_poly1305_update( &ctx->poly1305_ctx, aad_len, aad ) );
+}
+
+int mbedtls_aead_chacha20_poly1305_update( mbedtls_aead_chacha20_poly1305_context *ctx,
+                                           size_t len,
+                                           const unsigned char *input,
+                                           unsigned char *output )
+{
+    if ( ( ctx == NULL ) || ( input == NULL ) || ( output == NULL ) )
+    {
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+    }
+    else if ( ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_AAD ) &&
+              ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT ) )
+    {
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_STATE );
+    }
+
+    if ( ctx->state == AEAD_CHACHA20_POLY1305_STATE_AAD )
+    {
+        ctx->state = AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT;
+
+        mbedtls_aead_chacha20_poly1305_pad_aad( ctx );
+    }
+
+    ctx->ciphertext_len += len;
+
+    if ( ctx->mode == MBEDTLS_AEAD_CHACHA20_POLY1305_ENCRYPT )
+    {
+        /* Note: the following functions return an error only if one or more of
+         *       the input pointers are NULL. Since we have checked their validity
+         *       above, we can safety ignore the return value.
+         */
+        (void)mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
+        (void)mbedtls_poly1305_update( &ctx->poly1305_ctx, len, output );
+    }
+    else /* DECRYPT */
+    {
+        (void)mbedtls_poly1305_update( &ctx->poly1305_ctx, len, input );
+        (void)mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
+    }
+
+    return( 0 );
+}
+
+int mbedtls_aead_chacha20_poly1305_finish( mbedtls_aead_chacha20_poly1305_context *ctx,
+                                           unsigned char mac[16] )
+{
+    unsigned char len_block[16];
+
+    if ( ( ctx == NULL ) || ( mac == NULL ) )
+    {
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+    }
+    else if ( ctx->state == AEAD_CHACHA20_POLY1305_STATE_INIT )
+    {
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_STATE );
+    }
+
+    if ( ctx->state == AEAD_CHACHA20_POLY1305_STATE_AAD )
+    {
+        mbedtls_aead_chacha20_poly1305_pad_aad( ctx );
+    }
+    else if ( ctx->state == AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT )
+    {
+        mbedtls_aead_chacha20_poly1305_pad_ciphertext( ctx );
+    }
+
+    ctx->state = AEAD_CHACHA20_POLY1305_STATE_FINISHED;
+
+    /* The lengths of the AAD and ciphertext are processed by
+     * Poly1305 as the final 128-bit block, encoded as little-endian integers.
+     */
+    len_block[0]  = (unsigned char)ctx->aad_len;
+    len_block[1]  = (unsigned char)( ctx->aad_len >> 8 );
+    len_block[2]  = (unsigned char)( ctx->aad_len >> 16 );
+    len_block[3]  = (unsigned char)( ctx->aad_len >> 24 );
+    len_block[4]  = (unsigned char)( ctx->aad_len >> 32 );
+    len_block[5]  = (unsigned char)( ctx->aad_len >> 40 );
+    len_block[6]  = (unsigned char)( ctx->aad_len >> 48 );
+    len_block[7]  = (unsigned char)( ctx->aad_len >> 56 );
+    len_block[8]  = (unsigned char)ctx->ciphertext_len;
+    len_block[9]  = (unsigned char)( ctx->ciphertext_len >> 8 );
+    len_block[10] = (unsigned char)( ctx->ciphertext_len >> 16 );
+    len_block[11] = (unsigned char)( ctx->ciphertext_len >> 24 );
+    len_block[12] = (unsigned char)( ctx->ciphertext_len >> 32 );
+    len_block[13] = (unsigned char)( ctx->ciphertext_len >> 40 );
+    len_block[14] = (unsigned char)( ctx->ciphertext_len >> 48 );
+    len_block[15] = (unsigned char)( ctx->ciphertext_len >> 56 );
+
+    (void)mbedtls_poly1305_update( &ctx->poly1305_ctx, 16U, len_block );
+    (void)mbedtls_poly1305_finish( &ctx->poly1305_ctx, mac );
+
+    return( 0 );
+}
+
+#endif /* MBEDTLS_AEAD_CHACHA20_POLY1305_ALT */
+
+int mbedtls_aead_chacha20_poly1305_crypt_and_mac ( const unsigned char key[32],
+                                                    const unsigned char nonce[12],
+                                                    mbedtls_aead_chacha20_poly1305_mode_t mode,
+                                                    size_t aad_len,
+                                                    const unsigned char *aad,
+                                                    size_t ilen,
+                                                    const unsigned char *input,
+                                                    unsigned char *output,
+                                                    unsigned char mac[16] )
+{
+    mbedtls_aead_chacha20_poly1305_context ctx;
+    int result;
+
+    mbedtls_aead_chacha20_poly1305_init( &ctx );
+
+    result = mbedtls_aead_chacha20_poly1305_setkey( &ctx, key );
+    if ( result != 0 )
+        goto cleanup;
+
+    result = mbedtls_aead_chacha20_poly1305_starts( &ctx, nonce, mode );
+    if ( result != 0 )
+        goto cleanup;
+
+    result = mbedtls_aead_chacha20_poly1305_update_aad( &ctx, aad_len, aad );
+    if ( result != 0 )
+            goto cleanup;
+
+    result = mbedtls_aead_chacha20_poly1305_update( &ctx, ilen, input, output );
+    if ( result != 0 )
+            goto cleanup;
+
+    result = mbedtls_aead_chacha20_poly1305_finish( &ctx, mac );
+
+cleanup:
+    mbedtls_aead_chacha20_poly1305_free( &ctx );
+    return( result );
+}
+
+#if defined(MBEDTLS_SELF_TEST)
+
+static const unsigned char test_key[1][32] =
+{
+    {
+        0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+        0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+        0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
+        0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f
+    }
+};
+
+static const unsigned char test_nonce[1][12] =
+{
+    {
+        0x07, 0x00, 0x00, 0x00,                         /* 32-bit common part */
+        0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47  /* 64-bit IV */
+    }
+};
+
+static const unsigned char test_aad[1][12] =
+{
+    {
+        0x50, 0x51, 0x52, 0x53, 0xc0, 0xc1, 0xc2, 0xc3,
+        0xc4, 0xc5, 0xc6, 0xc7
+    }
+};
+
+static const size_t test_aad_len[1] =
+{
+    12U
+};
+
+static const unsigned char test_input[1][114] =
+{
+    {
+        0x4c, 0x61, 0x64, 0x69, 0x65, 0x73, 0x20, 0x61,
+        0x6e, 0x64, 0x20, 0x47, 0x65, 0x6e, 0x74, 0x6c,
+        0x65, 0x6d, 0x65, 0x6e, 0x20, 0x6f, 0x66, 0x20,
+        0x74, 0x68, 0x65, 0x20, 0x63, 0x6c, 0x61, 0x73,
+        0x73, 0x20, 0x6f, 0x66, 0x20, 0x27, 0x39, 0x39,
+        0x3a, 0x20, 0x49, 0x66, 0x20, 0x49, 0x20, 0x63,
+        0x6f, 0x75, 0x6c, 0x64, 0x20, 0x6f, 0x66, 0x66,
+        0x65, 0x72, 0x20, 0x79, 0x6f, 0x75, 0x20, 0x6f,
+        0x6e, 0x6c, 0x79, 0x20, 0x6f, 0x6e, 0x65, 0x20,
+        0x74, 0x69, 0x70, 0x20, 0x66, 0x6f, 0x72, 0x20,
+        0x74, 0x68, 0x65, 0x20, 0x66, 0x75, 0x74, 0x75,
+        0x72, 0x65, 0x2c, 0x20, 0x73, 0x75, 0x6e, 0x73,
+        0x63, 0x72, 0x65, 0x65, 0x6e, 0x20, 0x77, 0x6f,
+        0x75, 0x6c, 0x64, 0x20, 0x62, 0x65, 0x20, 0x69,
+        0x74, 0x2e
+    }
+};
+
+static const unsigned char test_output[1][114] =
+{
+    {
+        0xd3, 0x1a, 0x8d, 0x34, 0x64, 0x8e, 0x60, 0xdb,
+        0x7b, 0x86, 0xaf, 0xbc, 0x53, 0xef, 0x7e, 0xc2,
+        0xa4, 0xad, 0xed, 0x51, 0x29, 0x6e, 0x08, 0xfe,
+        0xa9, 0xe2, 0xb5, 0xa7, 0x36, 0xee, 0x62, 0xd6,
+        0x3d, 0xbe, 0xa4, 0x5e, 0x8c, 0xa9, 0x67, 0x12,
+        0x82, 0xfa, 0xfb, 0x69, 0xda, 0x92, 0x72, 0x8b,
+        0x1a, 0x71, 0xde, 0x0a, 0x9e, 0x06, 0x0b, 0x29,
+        0x05, 0xd6, 0xa5, 0xb6, 0x7e, 0xcd, 0x3b, 0x36,
+        0x92, 0xdd, 0xbd, 0x7f, 0x2d, 0x77, 0x8b, 0x8c,
+        0x98, 0x03, 0xae, 0xe3, 0x28, 0x09, 0x1b, 0x58,
+        0xfa, 0xb3, 0x24, 0xe4, 0xfa, 0xd6, 0x75, 0x94,
+        0x55, 0x85, 0x80, 0x8b, 0x48, 0x31, 0xd7, 0xbc,
+        0x3f, 0xf4, 0xde, 0xf0, 0x8e, 0x4b, 0x7a, 0x9d,
+        0xe5, 0x76, 0xd2, 0x65, 0x86, 0xce, 0xc6, 0x4b,
+        0x61, 0x16
+    }
+};
+
+static const size_t test_input_len[1] =
+{
+    114U
+};
+
+static const unsigned char test_mac[1][16] =
+{
+    {
+        0x1a, 0xe1, 0x0b, 0x59, 0x4f, 0x09, 0xe2, 0x6a,
+        0x7e, 0x90, 0x2e, 0xcb, 0xd0, 0x60, 0x06, 0x91
+    }
+};
+
+int mbedtls_aead_chacha20_poly1305_self_test( int verbose )
+{
+    size_t i;
+    int result;
+    unsigned char output[200];
+    unsigned char mac[16];
+
+    for ( i = 0U; i < 1U; i++ )
+    {
+        result = mbedtls_aead_chacha20_poly1305_crypt_and_mac( test_key[i],
+                                                               test_nonce[i],
+                                                               MBEDTLS_AEAD_CHACHA20_POLY1305_ENCRYPT,
+                                                               test_aad_len[i],
+                                                               test_aad[i],
+                                                               test_input_len[i],
+                                                               test_input[i],
+                                                               output,
+                                                               mac );
+        if ( result != 0 )
+        {
+            if ( verbose != 0 )
+            {
+                mbedtls_printf( "ChaCha20-Poly1305 test %zi error code: %i\n", i, result );
+            }
+            return( -1 );
+        }
+
+        if ( memcmp( output, test_output[i], test_input_len[i] ) != 0 )
+        {
+            if ( verbose != 0 )
+            {
+                mbedtls_printf( "ChaCha20-Poly1305 test %zi failure (wrong output)\n", i );
+            }
+            return( -1 );
+        }
+
+        if ( memcmp( mac, test_mac[i], 16U ) != 0 )
+        {
+            if ( verbose != 0 )
+            {
+                mbedtls_printf( "ChaCha20-Poly1305 test %zi failure (wrong MAC)\n", i );
+            }
+            return( -1 );
+        }
+    }
+
+    return( 0 );
+}
+
+#endif /* MBEDTLS_SELF_TEST */
+
+#endif /* MBEDTLS_AEAD_CHACHA20_POLY1305_C */
diff --git a/library/chacha20.c b/library/chacha20.c
index 8206a3b..b20c7ad 100644
--- a/library/chacha20.c
+++ b/library/chacha20.c
@@ -134,46 +134,47 @@
  * \param working_state This state is used as a temporary working area.
  * \param keystream     Generated keystream bytes are written to this buffer.
  */
-static void mbedtls_chacha20_block( mbedtls_chacha20_context *ctx,
+static void mbedtls_chacha20_block( const uint32_t initial_state[16],
+                                    uint32_t working_state[16],
                                     unsigned char keystream[64] )
 {
     size_t i;
     size_t offset;
 
-    memcpy( ctx->working_state,
-            ctx->initial_state,
-            sizeof(ctx->initial_state) );
+    memcpy( working_state,
+            initial_state,
+            CHACHA20_BLOCK_SIZE_BYTES );
 
     for ( i = 0U; i < 10U; i++ )
     {
-        mbedtls_chacha20_inner_block( ctx->working_state );
+        mbedtls_chacha20_inner_block( working_state );
     }
 
-    ctx->working_state[0]  += ctx->initial_state[0];
-    ctx->working_state[1]  += ctx->initial_state[1];
-    ctx->working_state[2]  += ctx->initial_state[2];
-    ctx->working_state[3]  += ctx->initial_state[3];
-    ctx->working_state[4]  += ctx->initial_state[4];
-    ctx->working_state[5]  += ctx->initial_state[5];
-    ctx->working_state[6]  += ctx->initial_state[6];
-    ctx->working_state[7]  += ctx->initial_state[7];
-    ctx->working_state[8]  += ctx->initial_state[8];
-    ctx->working_state[9]  += ctx->initial_state[9];
-    ctx->working_state[10] += ctx->initial_state[10];
-    ctx->working_state[11] += ctx->initial_state[11];
-    ctx->working_state[12] += ctx->initial_state[12];
-    ctx->working_state[13] += ctx->initial_state[13];
-    ctx->working_state[14] += ctx->initial_state[14];
-    ctx->working_state[15] += ctx->initial_state[15];
+    working_state[0]  += initial_state[0];
+    working_state[1]  += initial_state[1];
+    working_state[2]  += initial_state[2];
+    working_state[3]  += initial_state[3];
+    working_state[4]  += initial_state[4];
+    working_state[5]  += initial_state[5];
+    working_state[6]  += initial_state[6];
+    working_state[7]  += initial_state[7];
+    working_state[8]  += initial_state[8];
+    working_state[9]  += initial_state[9];
+    working_state[10] += initial_state[10];
+    working_state[11] += initial_state[11];
+    working_state[12] += initial_state[12];
+    working_state[13] += initial_state[13];
+    working_state[14] += initial_state[14];
+    working_state[15] += initial_state[15];
 
     for ( i = 0U; i < 16; i++ )
     {
         offset = i * 4U;
 
-        keystream[offset     ] = (unsigned char)  ctx->working_state[i];
-        keystream[offset + 1U] = (unsigned char)( ctx->working_state[i] >> 8  );
-        keystream[offset + 2U] = (unsigned char)( ctx->working_state[i] >> 16 );
-        keystream[offset + 3U] = (unsigned char)( ctx->working_state[i] >> 24 );
+        keystream[offset     ] = (unsigned char)  working_state[i];
+        keystream[offset + 1U] = (unsigned char)( working_state[i] >> 8  );
+        keystream[offset + 2U] = (unsigned char)( working_state[i] >> 16 );
+        keystream[offset + 3U] = (unsigned char)( working_state[i] >> 24 );
     }
 }
 
@@ -245,6 +246,43 @@
     return( 0 );
 }
 
+int mbedtls_chacha20_keystream_block( const mbedtls_chacha20_context *ctx,
+                                      uint32_t counter,
+                                      unsigned char keystream[64] )
+{
+    uint32_t initial_state[16];
+    uint32_t working_state[16];
+
+    if ( ( ctx == NULL ) || ( keystream == NULL ) )
+    {
+        return( MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA );
+    }
+
+    initial_state[0]  = ctx->initial_state[0];
+    initial_state[1]  = ctx->initial_state[1];
+    initial_state[2]  = ctx->initial_state[2];
+    initial_state[3]  = ctx->initial_state[3];
+    initial_state[4]  = ctx->initial_state[4];
+    initial_state[5]  = ctx->initial_state[5];
+    initial_state[6]  = ctx->initial_state[6];
+    initial_state[7]  = ctx->initial_state[7];
+    initial_state[8]  = ctx->initial_state[8];
+    initial_state[9]  = ctx->initial_state[9];
+    initial_state[10] = ctx->initial_state[10];
+    initial_state[11] = ctx->initial_state[11];
+    initial_state[12] = counter;
+    initial_state[13] = ctx->initial_state[13];
+    initial_state[14] = ctx->initial_state[14];
+    initial_state[15] = ctx->initial_state[15];
+
+    mbedtls_chacha20_block( initial_state, working_state, keystream );
+
+    mbedtls_zeroize( initial_state, sizeof(initial_state) );
+    mbedtls_zeroize( working_state, sizeof(working_state) );
+
+    return ( 0 );
+}
+
 int mbedtls_chacha20_update( mbedtls_chacha20_context *ctx,
                               size_t size,
                               const unsigned char *input,
@@ -271,7 +309,7 @@
     /* Process full blocks */
     while ( size >= CHACHA20_BLOCK_SIZE_BYTES )
     {
-        mbedtls_chacha20_block( ctx, &output[offset] );
+        mbedtls_chacha20_block( ctx->initial_state, ctx->working_state, &output[offset] );
 
         for ( i = 0U; i < 64U; i += 8U )
         {
@@ -288,14 +326,14 @@
         /* Increment counter */
         ctx->initial_state[CHACHA20_CTR_INDEX]++;
 
-        offset += 64U;
-        size   -= 64U;
+        offset += CHACHA20_BLOCK_SIZE_BYTES;
+        size   -= CHACHA20_BLOCK_SIZE_BYTES;
     }
 
     /* Last (partial) block */
     if ( size > 0U )
     {
-        mbedtls_chacha20_block( ctx, ctx->keystream8 );
+        mbedtls_chacha20_block( ctx->initial_state, ctx->working_state, ctx->keystream8 );
 
         for ( i = 0U; i < size; i++)
         {
diff --git a/library/error.c b/library/error.c
index 12bd210..d0a75ca 100644
--- a/library/error.c
+++ b/library/error.c
@@ -41,6 +41,10 @@
 
 #include <stdio.h>
 
+#if defined(MBEDTLS_AEAD_CHACHA20_POLY1305_C)
+#include "mbedtls/aead_chacha20_poly1305.h"
+#endif
+
 #if defined(MBEDTLS_AES_C)
 #include "mbedtls/aes.h"
 #endif
@@ -575,6 +579,13 @@
     // Low level error codes
     //
     // BEGIN generated code
+#if defined(MBEDTLS_AEAD_CHACHA20_POLY1305_C)
+    if( use_ret == -(MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA) )
+        mbedtls_snprintf( buf, buflen, "AEAD_CHACHA20_POLY1305 - Invalid input parameter(s)" );
+    if( use_ret == -(MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_STATE) )
+        mbedtls_snprintf( buf, buflen, "AEAD_CHACHA20_POLY1305 - The requested operation is not permitted in the current state" );
+#endif /* MBEDTLS_AEAD_CHACHA20_POLY1305_C */
+
 #if defined(MBEDTLS_AES_C)
     if( use_ret == -(MBEDTLS_ERR_AES_INVALID_KEY_LENGTH) )
         mbedtls_snprintf( buf, buflen, "AES - Invalid key length" );
diff --git a/library/version_features.c b/library/version_features.c
index babf2c7..64aa9f6 100644
--- a/library/version_features.c
+++ b/library/version_features.c
@@ -516,6 +516,9 @@
 #if defined(MBEDTLS_AES_C)
     "MBEDTLS_AES_C",
 #endif /* MBEDTLS_AES_C */
+#if defined(MBEDTLS_AEAD_CHACHA20_POLY1305_C)
+    "MBEDTLS_AEAD_CHACHA20_POLY1305_C",
+#endif /* MBEDTLS_AEAD_CHACHA20_POLY1305_C */
 #if defined(MBEDTLS_ARC4_C)
     "MBEDTLS_ARC4_C",
 #endif /* MBEDTLS_ARC4_C */