diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
new file mode 100644
index 0000000..5dde239
--- /dev/null
+++ b/include/mbedtls/ssl_internal.h
@@ -0,0 +1,819 @@
+/**
+ * \file ssl_internal.h
+ *
+ * \brief Internal functions shared by the SSL modules
+ */
+/*
+ *  Copyright (C) 2006-2015, 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_SSL_INTERNAL_H
+#define MBEDTLS_SSL_INTERNAL_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#include "ssl.h"
+#include "cipher.h"
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+#include "psa/crypto.h"
+#endif
+
+#if defined(MBEDTLS_MD5_C)
+#include "md5.h"
+#endif
+
+#if defined(MBEDTLS_SHA1_C)
+#include "sha1.h"
+#endif
+
+#if defined(MBEDTLS_SHA256_C)
+#include "sha256.h"
+#endif
+
+#if defined(MBEDTLS_SHA512_C)
+#include "sha512.h"
+#endif
+
+#if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
+#include "ecjpake.h"
+#endif
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+#include "psa/crypto.h"
+#include "psa_util.h"
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+
+#if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
+    !defined(inline) && !defined(__cplusplus)
+#define inline __inline
+#endif
+
+/* Determine minimum supported version */
+#define MBEDTLS_SSL_MIN_MAJOR_VERSION           MBEDTLS_SSL_MAJOR_VERSION_3
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+#define MBEDTLS_SSL_MIN_MINOR_VERSION           MBEDTLS_SSL_MINOR_VERSION_0
+#else
+#if defined(MBEDTLS_SSL_PROTO_TLS1)
+#define MBEDTLS_SSL_MIN_MINOR_VERSION           MBEDTLS_SSL_MINOR_VERSION_1
+#else
+#if defined(MBEDTLS_SSL_PROTO_TLS1_1)
+#define MBEDTLS_SSL_MIN_MINOR_VERSION           MBEDTLS_SSL_MINOR_VERSION_2
+#else
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+#define MBEDTLS_SSL_MIN_MINOR_VERSION           MBEDTLS_SSL_MINOR_VERSION_3
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+#endif /* MBEDTLS_SSL_PROTO_TLS1_1 */
+#endif /* MBEDTLS_SSL_PROTO_TLS1   */
+#endif /* MBEDTLS_SSL_PROTO_SSL3   */
+
+#define MBEDTLS_SSL_MIN_VALID_MINOR_VERSION MBEDTLS_SSL_MINOR_VERSION_1
+#define MBEDTLS_SSL_MIN_VALID_MAJOR_VERSION MBEDTLS_SSL_MAJOR_VERSION_3
+
+/* Determine maximum supported version */
+#define MBEDTLS_SSL_MAX_MAJOR_VERSION           MBEDTLS_SSL_MAJOR_VERSION_3
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+#define MBEDTLS_SSL_MAX_MINOR_VERSION           MBEDTLS_SSL_MINOR_VERSION_3
+#else
+#if defined(MBEDTLS_SSL_PROTO_TLS1_1)
+#define MBEDTLS_SSL_MAX_MINOR_VERSION           MBEDTLS_SSL_MINOR_VERSION_2
+#else
+#if defined(MBEDTLS_SSL_PROTO_TLS1)
+#define MBEDTLS_SSL_MAX_MINOR_VERSION           MBEDTLS_SSL_MINOR_VERSION_1
+#else
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+#define MBEDTLS_SSL_MAX_MINOR_VERSION           MBEDTLS_SSL_MINOR_VERSION_0
+#endif /* MBEDTLS_SSL_PROTO_SSL3   */
+#endif /* MBEDTLS_SSL_PROTO_TLS1   */
+#endif /* MBEDTLS_SSL_PROTO_TLS1_1 */
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+
+/* Shorthand for restartable ECC */
+#if defined(MBEDTLS_ECP_RESTARTABLE) && \
+    defined(MBEDTLS_SSL_CLI_C) && \
+    defined(MBEDTLS_SSL_PROTO_TLS1_2) && \
+    defined(MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED)
+#define MBEDTLS_SSL__ECP_RESTARTABLE
+#endif
+
+#define MBEDTLS_SSL_INITIAL_HANDSHAKE           0
+#define MBEDTLS_SSL_RENEGOTIATION_IN_PROGRESS   1   /* In progress */
+#define MBEDTLS_SSL_RENEGOTIATION_DONE          2   /* Done or aborted */
+#define MBEDTLS_SSL_RENEGOTIATION_PENDING       3   /* Requested (server only) */
+
+/*
+ * DTLS retransmission states, see RFC 6347 4.2.4
+ *
+ * The SENDING state is merged in PREPARING for initial sends,
+ * but is distinct for resends.
+ *
+ * Note: initial state is wrong for server, but is not used anyway.
+ */
+#define MBEDTLS_SSL_RETRANS_PREPARING       0
+#define MBEDTLS_SSL_RETRANS_SENDING         1
+#define MBEDTLS_SSL_RETRANS_WAITING         2
+#define MBEDTLS_SSL_RETRANS_FINISHED        3
+
+/*
+ * Allow extra bytes for record, authentication and encryption overhead:
+ * counter (8) + header (5) + IV(16) + MAC (16-48) + padding (0-256)
+ * and allow for a maximum of 1024 of compression expansion if
+ * enabled.
+ */
+#if defined(MBEDTLS_ZLIB_SUPPORT)
+#define MBEDTLS_SSL_COMPRESSION_ADD          1024
+#else
+#define MBEDTLS_SSL_COMPRESSION_ADD             0
+#endif
+
+#if defined(MBEDTLS_ARC4_C) || defined(MBEDTLS_CIPHER_MODE_CBC)
+/* Ciphersuites using HMAC */
+#if defined(MBEDTLS_SHA512_C)
+#define MBEDTLS_SSL_MAC_ADD                 48  /* SHA-384 used for HMAC */
+#elif defined(MBEDTLS_SHA256_C)
+#define MBEDTLS_SSL_MAC_ADD                 32  /* SHA-256 used for HMAC */
+#else
+#define MBEDTLS_SSL_MAC_ADD                 20  /* SHA-1   used for HMAC */
+#endif
+#else
+/* AEAD ciphersuites: GCM and CCM use a 128 bits tag */
+#define MBEDTLS_SSL_MAC_ADD                 16
+#endif
+
+#if defined(MBEDTLS_CIPHER_MODE_CBC)
+#define MBEDTLS_SSL_PADDING_ADD            256
+#else
+#define MBEDTLS_SSL_PADDING_ADD              0
+#endif
+
+#define MBEDTLS_SSL_PAYLOAD_OVERHEAD ( MBEDTLS_SSL_COMPRESSION_ADD +    \
+                                       MBEDTLS_MAX_IV_LENGTH +          \
+                                       MBEDTLS_SSL_MAC_ADD +            \
+                                       MBEDTLS_SSL_PADDING_ADD          \
+                                       )
+
+#define MBEDTLS_SSL_IN_PAYLOAD_LEN ( MBEDTLS_SSL_PAYLOAD_OVERHEAD + \
+                                     ( MBEDTLS_SSL_IN_CONTENT_LEN ) )
+
+#define MBEDTLS_SSL_OUT_PAYLOAD_LEN ( MBEDTLS_SSL_PAYLOAD_OVERHEAD + \
+                                      ( MBEDTLS_SSL_OUT_CONTENT_LEN ) )
+
+/* The maximum number of buffered handshake messages. */
+#define MBEDTLS_SSL_MAX_BUFFERED_HS 4
+
+/* Maximum length we can advertise as our max content length for
+   RFC 6066 max_fragment_length extension negotiation purposes
+   (the lesser of both sizes, if they are unequal.)
+ */
+#define MBEDTLS_TLS_EXT_ADV_CONTENT_LEN (                            \
+        (MBEDTLS_SSL_IN_CONTENT_LEN > MBEDTLS_SSL_OUT_CONTENT_LEN)   \
+        ? ( MBEDTLS_SSL_OUT_CONTENT_LEN )                            \
+        : ( MBEDTLS_SSL_IN_CONTENT_LEN )                             \
+        )
+
+/*
+ * Check that we obey the standard's message size bounds
+ */
+
+#if MBEDTLS_SSL_MAX_CONTENT_LEN > 16384
+#error "Bad configuration - record content too large."
+#endif
+
+#if MBEDTLS_SSL_IN_CONTENT_LEN > MBEDTLS_SSL_MAX_CONTENT_LEN
+#error "Bad configuration - incoming record content should not be larger than MBEDTLS_SSL_MAX_CONTENT_LEN."
+#endif
+
+#if MBEDTLS_SSL_OUT_CONTENT_LEN > MBEDTLS_SSL_MAX_CONTENT_LEN
+#error "Bad configuration - outgoing record content should not be larger than MBEDTLS_SSL_MAX_CONTENT_LEN."
+#endif
+
+#if MBEDTLS_SSL_IN_PAYLOAD_LEN > MBEDTLS_SSL_MAX_CONTENT_LEN + 2048
+#error "Bad configuration - incoming protected record payload too large."
+#endif
+
+#if MBEDTLS_SSL_OUT_PAYLOAD_LEN > MBEDTLS_SSL_MAX_CONTENT_LEN + 2048
+#error "Bad configuration - outgoing protected record payload too large."
+#endif
+
+/* Calculate buffer sizes */
+
+/* Note: Even though the TLS record header is only 5 bytes
+   long, we're internally using 8 bytes to store the
+   implicit sequence number. */
+#define MBEDTLS_SSL_HEADER_LEN 13
+
+#define MBEDTLS_SSL_IN_BUFFER_LEN  \
+    ( ( MBEDTLS_SSL_HEADER_LEN ) + ( MBEDTLS_SSL_IN_PAYLOAD_LEN ) )
+
+#define MBEDTLS_SSL_OUT_BUFFER_LEN  \
+    ( ( MBEDTLS_SSL_HEADER_LEN ) + ( MBEDTLS_SSL_OUT_PAYLOAD_LEN ) )
+
+#ifdef MBEDTLS_ZLIB_SUPPORT
+/* Compression buffer holds both IN and OUT buffers, so should be size of the larger */
+#define MBEDTLS_SSL_COMPRESS_BUFFER_LEN (                               \
+        ( MBEDTLS_SSL_IN_BUFFER_LEN > MBEDTLS_SSL_OUT_BUFFER_LEN )      \
+        ? MBEDTLS_SSL_IN_BUFFER_LEN                                     \
+        : MBEDTLS_SSL_OUT_BUFFER_LEN                                    \
+        )
+#endif
+
+/*
+ * TLS extension flags (for extensions with outgoing ServerHello content
+ * that need it (e.g. for RENEGOTIATION_INFO the server already knows because
+ * of state of the renegotiation flag, so no indicator is required)
+ */
+#define MBEDTLS_TLS_EXT_SUPPORTED_POINT_FORMATS_PRESENT (1 << 0)
+#define MBEDTLS_TLS_EXT_ECJPAKE_KKPP_OK                 (1 << 1)
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2) && \
+    defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)
+/*
+ * Abstraction for a grid of allowed signature-hash-algorithm pairs.
+ */
+struct mbedtls_ssl_sig_hash_set_t
+{
+    /* At the moment, we only need to remember a single suitable
+     * hash algorithm per signature algorithm. As long as that's
+     * the case - and we don't need a general lookup function -
+     * we can implement the sig-hash-set as a map from signatures
+     * to hash algorithms. */
+    mbedtls_md_type_t rsa;
+    mbedtls_md_type_t ecdsa;
+};
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 &&
+          MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED */
+
+/*
+ * This structure contains the parameters only needed during handshake.
+ */
+struct mbedtls_ssl_handshake_params
+{
+    /*
+     * Handshake specific crypto variables
+     */
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2) && \
+    defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)
+    mbedtls_ssl_sig_hash_set_t hash_algs;             /*!<  Set of suitable sig-hash pairs */
+#endif
+#if defined(MBEDTLS_DHM_C)
+    mbedtls_dhm_context dhm_ctx;                /*!<  DHM key exchange        */
+#endif
+#if defined(MBEDTLS_ECDH_C)
+    mbedtls_ecdh_context ecdh_ctx;              /*!<  ECDH key exchange       */
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    psa_ecc_curve_t ecdh_psa_curve;
+    psa_key_handle_t ecdh_psa_privkey;
+    unsigned char ecdh_psa_peerkey[MBEDTLS_PSA_MAX_EC_PUBKEY_LENGTH];
+    size_t ecdh_psa_peerkey_len;
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+#endif /* MBEDTLS_ECDH_C */
+
+#if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
+    mbedtls_ecjpake_context ecjpake_ctx;        /*!< EC J-PAKE key exchange */
+#if defined(MBEDTLS_SSL_CLI_C)
+    unsigned char *ecjpake_cache;               /*!< Cache for ClientHello ext */
+    size_t ecjpake_cache_len;                   /*!< Length of cached data */
+#endif
+#endif /* MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED */
+#if defined(MBEDTLS_ECDH_C) || defined(MBEDTLS_ECDSA_C) || \
+    defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
+    const mbedtls_ecp_curve_info **curves;      /*!<  Supported elliptic curves */
+#endif
+#if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    psa_key_handle_t psk_opaque;        /*!< Opaque PSK from the callback   */
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+    unsigned char *psk;                 /*!<  PSK from the callback         */
+    size_t psk_len;                     /*!<  Length of PSK from callback   */
+#endif /* MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED */
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+    mbedtls_ssl_key_cert *key_cert;     /*!< chosen key/cert pair (server)  */
+#if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
+    int sni_authmode;                   /*!< authmode from SNI callback     */
+    mbedtls_ssl_key_cert *sni_key_cert; /*!< key/cert list from SNI         */
+    mbedtls_x509_crt *sni_ca_chain;     /*!< trusted CAs from SNI callback  */
+    mbedtls_x509_crl *sni_ca_crl;       /*!< trusted CAs CRLs from SNI      */
+#endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
+#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
+    int ecrs_enabled;                   /*!< Handshake supports EC restart? */
+    mbedtls_x509_crt_restart_ctx ecrs_ctx;  /*!< restart context            */
+    enum { /* this complements ssl->state with info on intra-state operations */
+        ssl_ecrs_none = 0,              /*!< nothing going on (yet)         */
+        ssl_ecrs_crt_verify,            /*!< Certificate: crt_verify()      */
+        ssl_ecrs_ske_start_processing,  /*!< ServerKeyExchange: pk_verify() */
+        ssl_ecrs_cke_ecdh_calc_secret,  /*!< ClientKeyExchange: ECDH step 2 */
+        ssl_ecrs_crt_vrfy_sign,         /*!< CertificateVerify: pk_sign()   */
+    } ecrs_state;                       /*!< current (or last) operation    */
+    mbedtls_x509_crt *ecrs_peer_cert;   /*!< The peer's CRT chain.          */
+    size_t ecrs_n;                      /*!< place for saving a length      */
+#endif
+#if defined(MBEDTLS_X509_CRT_PARSE_C) && \
+    !defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
+    mbedtls_pk_context peer_pubkey;     /*!< The public key from the peer.  */
+#endif /* MBEDTLS_X509_CRT_PARSE_C && !MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    unsigned int out_msg_seq;           /*!<  Outgoing handshake sequence number */
+    unsigned int in_msg_seq;            /*!<  Incoming handshake sequence number */
+
+    unsigned char *verify_cookie;       /*!<  Cli: HelloVerifyRequest cookie
+                                              Srv: unused                    */
+    unsigned char verify_cookie_len;    /*!<  Cli: cookie length
+                                              Srv: flag for sending a cookie */
+
+    uint32_t retransmit_timeout;        /*!<  Current value of timeout       */
+    unsigned char retransmit_state;     /*!<  Retransmission state           */
+    mbedtls_ssl_flight_item *flight;    /*!<  Current outgoing flight        */
+    mbedtls_ssl_flight_item *cur_msg;   /*!<  Current message in flight      */
+    unsigned char *cur_msg_p;           /*!<  Position in current message    */
+    unsigned int in_flight_start_seq;   /*!<  Minimum message sequence in the
+                                              flight being received          */
+    mbedtls_ssl_transform *alt_transform_out;   /*!<  Alternative transform for
+                                              resending messages             */
+    unsigned char alt_out_ctr[8];       /*!<  Alternative record epoch/counter
+                                              for resending messages         */
+
+    struct
+    {
+        size_t total_bytes_buffered; /*!< Cumulative size of heap allocated
+                                      *   buffers used for message buffering. */
+
+        uint8_t seen_ccs;               /*!< Indicates if a CCS message has
+                                         *   been seen in the current flight. */
+
+        struct mbedtls_ssl_hs_buffer
+        {
+            unsigned is_valid      : 1;
+            unsigned is_fragmented : 1;
+            unsigned is_complete   : 1;
+            unsigned char *data;
+            size_t data_len;
+        } hs[MBEDTLS_SSL_MAX_BUFFERED_HS];
+
+        struct
+        {
+            unsigned char *data;
+            size_t len;
+            unsigned epoch;
+        } future_record;
+
+    } buffering;
+
+    uint16_t mtu;                       /*!<  Handshake mtu, used to fragment outgoing messages */
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+    /*
+     * Checksum contexts
+     */
+#if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) || \
+    defined(MBEDTLS_SSL_PROTO_TLS1_1)
+       mbedtls_md5_context fin_md5;
+      mbedtls_sha1_context fin_sha1;
+#endif
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+#if defined(MBEDTLS_SHA256_C)
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    psa_hash_operation_t fin_sha256_psa;
+#else
+    mbedtls_sha256_context fin_sha256;
+#endif
+#endif
+#if defined(MBEDTLS_SHA512_C)
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    psa_hash_operation_t fin_sha384_psa;
+#else
+    mbedtls_sha512_context fin_sha512;
+#endif
+#endif
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+
+    void (*update_checksum)(mbedtls_ssl_context *, const unsigned char *, size_t);
+    void (*calc_verify)(mbedtls_ssl_context *, unsigned char *);
+    void (*calc_finished)(mbedtls_ssl_context *, unsigned char *, int);
+    int  (*tls_prf)(const unsigned char *, size_t, const char *,
+                    const unsigned char *, size_t,
+                    unsigned char *, size_t);
+
+    size_t pmslen;                      /*!<  premaster length        */
+
+    unsigned char randbytes[64];        /*!<  random bytes            */
+    unsigned char premaster[MBEDTLS_PREMASTER_SIZE];
+                                        /*!<  premaster secret        */
+
+    int resume;                         /*!<  session resume indicator*/
+    int max_major_ver;                  /*!< max. major version client*/
+    int max_minor_ver;                  /*!< max. minor version client*/
+    int cli_exts;                       /*!< client extension presence*/
+
+#if defined(MBEDTLS_SSL_SESSION_TICKETS)
+    int new_session_ticket;             /*!< use NewSessionTicket?    */
+#endif /* MBEDTLS_SSL_SESSION_TICKETS */
+#if defined(MBEDTLS_SSL_EXTENDED_MASTER_SECRET)
+    int extended_ms;                    /*!< use Extended Master Secret? */
+#endif
+
+#if defined(MBEDTLS_SSL_ASYNC_PRIVATE)
+    unsigned int async_in_progress : 1; /*!< an asynchronous operation is in progress */
+#endif /* MBEDTLS_SSL_ASYNC_PRIVATE */
+
+#if defined(MBEDTLS_SSL_ASYNC_PRIVATE)
+    /** Asynchronous operation context. This field is meant for use by the
+     * asynchronous operation callbacks (mbedtls_ssl_config::f_async_sign_start,
+     * mbedtls_ssl_config::f_async_decrypt_start,
+     * mbedtls_ssl_config::f_async_resume, mbedtls_ssl_config::f_async_cancel).
+     * The library does not use it internally. */
+    void *user_async_ctx;
+#endif /* MBEDTLS_SSL_ASYNC_PRIVATE */
+};
+
+typedef struct mbedtls_ssl_hs_buffer mbedtls_ssl_hs_buffer;
+
+/*
+ * This structure contains a full set of runtime transform parameters
+ * either in negotiation or active.
+ */
+struct mbedtls_ssl_transform
+{
+    /*
+     * Session specific crypto layer
+     */
+    const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
+                                        /*!<  Chosen cipersuite_info  */
+    unsigned int keylen;                /*!<  symmetric key length (bytes)  */
+    size_t minlen;                      /*!<  min. ciphertext length  */
+    size_t ivlen;                       /*!<  IV length               */
+    size_t fixed_ivlen;                 /*!<  Fixed part of IV (AEAD) */
+    size_t maclen;                      /*!<  MAC length              */
+
+    unsigned char iv_enc[16];           /*!<  IV (encryption)         */
+    unsigned char iv_dec[16];           /*!<  IV (decryption)         */
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+    /* Needed only for SSL v3.0 secret */
+    unsigned char mac_enc[20];          /*!<  SSL v3.0 secret (enc)   */
+    unsigned char mac_dec[20];          /*!<  SSL v3.0 secret (dec)   */
+#endif /* MBEDTLS_SSL_PROTO_SSL3 */
+
+    mbedtls_md_context_t md_ctx_enc;            /*!<  MAC (encryption)        */
+    mbedtls_md_context_t md_ctx_dec;            /*!<  MAC (decryption)        */
+
+    mbedtls_cipher_context_t cipher_ctx_enc;    /*!<  encryption context      */
+    mbedtls_cipher_context_t cipher_ctx_dec;    /*!<  decryption context      */
+
+    /*
+     * Session specific compression layer
+     */
+#if defined(MBEDTLS_ZLIB_SUPPORT)
+    z_stream ctx_deflate;               /*!<  compression context     */
+    z_stream ctx_inflate;               /*!<  decompression context   */
+#endif
+};
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+/*
+ * List of certificate + private key pairs
+ */
+struct mbedtls_ssl_key_cert
+{
+    mbedtls_x509_crt *cert;                 /*!< cert                       */
+    mbedtls_pk_context *key;                /*!< private key                */
+    mbedtls_ssl_key_cert *next;             /*!< next key/cert pair         */
+};
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+/*
+ * List of handshake messages kept around for resending
+ */
+struct mbedtls_ssl_flight_item
+{
+    unsigned char *p;       /*!< message, including handshake headers   */
+    size_t len;             /*!< length of p                            */
+    unsigned char type;     /*!< type of the message: handshake or CCS  */
+    mbedtls_ssl_flight_item *next;  /*!< next handshake message(s)              */
+};
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2) && \
+    defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)
+
+/* Find an entry in a signature-hash set matching a given hash algorithm. */
+mbedtls_md_type_t mbedtls_ssl_sig_hash_set_find( mbedtls_ssl_sig_hash_set_t *set,
+                                                 mbedtls_pk_type_t sig_alg );
+/* Add a signature-hash-pair to a signature-hash set */
+void mbedtls_ssl_sig_hash_set_add( mbedtls_ssl_sig_hash_set_t *set,
+                                   mbedtls_pk_type_t sig_alg,
+                                   mbedtls_md_type_t md_alg );
+/* Allow exactly one hash algorithm for each signature. */
+void mbedtls_ssl_sig_hash_set_const_hash( mbedtls_ssl_sig_hash_set_t *set,
+                                          mbedtls_md_type_t md_alg );
+
+/* Setup an empty signature-hash set */
+static inline void mbedtls_ssl_sig_hash_set_init( mbedtls_ssl_sig_hash_set_t *set )
+{
+    mbedtls_ssl_sig_hash_set_const_hash( set, MBEDTLS_MD_NONE );
+}
+
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2) &&
+          MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED */
+
+/**
+ * \brief           Free referenced items in an SSL transform context and clear
+ *                  memory
+ *
+ * \param transform SSL transform context
+ */
+void mbedtls_ssl_transform_free( mbedtls_ssl_transform *transform );
+
+/**
+ * \brief           Free referenced items in an SSL handshake context and clear
+ *                  memory
+ *
+ * \param ssl       SSL context
+ */
+void mbedtls_ssl_handshake_free( mbedtls_ssl_context *ssl );
+
+int mbedtls_ssl_handshake_client_step( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_handshake_server_step( mbedtls_ssl_context *ssl );
+void mbedtls_ssl_handshake_wrapup( mbedtls_ssl_context *ssl );
+
+int mbedtls_ssl_send_fatal_handshake_failure( mbedtls_ssl_context *ssl );
+
+void mbedtls_ssl_reset_checksum( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl );
+
+int mbedtls_ssl_handle_message_type( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_prepare_handshake_record( mbedtls_ssl_context *ssl );
+void mbedtls_ssl_update_handshake_status( mbedtls_ssl_context *ssl );
+
+/**
+ * \brief       Update record layer
+ *
+ *              This function roughly separates the implementation
+ *              of the logic of (D)TLS from the implementation
+ *              of the secure transport.
+ *
+ * \param  ssl              The SSL context to use.
+ * \param  update_hs_digest This indicates if the handshake digest
+ *                          should be automatically updated in case
+ *                          a handshake message is found.
+ *
+ * \return      0 or non-zero error code.
+ *
+ * \note        A clarification on what is called 'record layer' here
+ *              is in order, as many sensible definitions are possible:
+ *
+ *              The record layer takes as input an untrusted underlying
+ *              transport (stream or datagram) and transforms it into
+ *              a serially multiplexed, secure transport, which
+ *              conceptually provides the following:
+ *
+ *              (1) Three datagram based, content-agnostic transports
+ *                  for handshake, alert and CCS messages.
+ *              (2) One stream- or datagram-based transport
+ *                  for application data.
+ *              (3) Functionality for changing the underlying transform
+ *                  securing the contents.
+ *
+ *              The interface to this functionality is given as follows:
+ *
+ *              a Updating
+ *                [Currently implemented by mbedtls_ssl_read_record]
+ *
+ *                Check if and on which of the four 'ports' data is pending:
+ *                Nothing, a controlling datagram of type (1), or application
+ *                data (2). In any case data is present, internal buffers
+ *                provide access to the data for the user to process it.
+ *                Consumption of type (1) datagrams is done automatically
+ *                on the next update, invalidating that the internal buffers
+ *                for previous datagrams, while consumption of application
+ *                data (2) is user-controlled.
+ *
+ *              b Reading of application data
+ *                [Currently manual adaption of ssl->in_offt pointer]
+ *
+ *                As mentioned in the last paragraph, consumption of data
+ *                is different from the automatic consumption of control
+ *                datagrams (1) because application data is treated as a stream.
+ *
+ *              c Tracking availability of application data
+ *                [Currently manually through decreasing ssl->in_msglen]
+ *
+ *                For efficiency and to retain datagram semantics for
+ *                application data in case of DTLS, the record layer
+ *                provides functionality for checking how much application
+ *                data is still available in the internal buffer.
+ *
+ *              d Changing the transformation securing the communication.
+ *
+ *              Given an opaque implementation of the record layer in the
+ *              above sense, it should be possible to implement the logic
+ *              of (D)TLS on top of it without the need to know anything
+ *              about the record layer's internals. This is done e.g.
+ *              in all the handshake handling functions, and in the
+ *              application data reading function mbedtls_ssl_read.
+ *
+ * \note        The above tries to give a conceptual picture of the
+ *              record layer, but the current implementation deviates
+ *              from it in some places. For example, our implementation of
+ *              the update functionality through mbedtls_ssl_read_record
+ *              discards datagrams depending on the current state, which
+ *              wouldn't fall under the record layer's responsibility
+ *              following the above definition.
+ *
+ */
+int mbedtls_ssl_read_record( mbedtls_ssl_context *ssl,
+                             unsigned update_hs_digest );
+int mbedtls_ssl_fetch_input( mbedtls_ssl_context *ssl, size_t nb_want );
+
+int mbedtls_ssl_write_handshake_msg( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl, uint8_t force_flush );
+int mbedtls_ssl_flush_output( mbedtls_ssl_context *ssl );
+
+int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_write_certificate( mbedtls_ssl_context *ssl );
+
+int mbedtls_ssl_parse_change_cipher_spec( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_write_change_cipher_spec( mbedtls_ssl_context *ssl );
+
+int mbedtls_ssl_parse_finished( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_write_finished( mbedtls_ssl_context *ssl );
+
+void mbedtls_ssl_optimize_checksum( mbedtls_ssl_context *ssl,
+                            const mbedtls_ssl_ciphersuite_t *ciphersuite_info );
+
+#if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
+int mbedtls_ssl_psk_derive_premaster( mbedtls_ssl_context *ssl, mbedtls_key_exchange_type_t key_ex );
+#endif
+
+#if defined(MBEDTLS_PK_C)
+unsigned char mbedtls_ssl_sig_from_pk( mbedtls_pk_context *pk );
+unsigned char mbedtls_ssl_sig_from_pk_alg( mbedtls_pk_type_t type );
+mbedtls_pk_type_t mbedtls_ssl_pk_alg_from_sig( unsigned char sig );
+#endif
+
+mbedtls_md_type_t mbedtls_ssl_md_alg_from_hash( unsigned char hash );
+unsigned char mbedtls_ssl_hash_from_md_alg( int md );
+int mbedtls_ssl_set_calc_verify_md( mbedtls_ssl_context *ssl, int md );
+
+#if defined(MBEDTLS_ECP_C)
+int mbedtls_ssl_check_curve( const mbedtls_ssl_context *ssl, mbedtls_ecp_group_id grp_id );
+#endif
+
+#if defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)
+int mbedtls_ssl_check_sig_hash( const mbedtls_ssl_context *ssl,
+                                mbedtls_md_type_t md );
+#endif
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+static inline mbedtls_pk_context *mbedtls_ssl_own_key( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_key_cert *key_cert;
+
+    if( ssl->handshake != NULL && ssl->handshake->key_cert != NULL )
+        key_cert = ssl->handshake->key_cert;
+    else
+        key_cert = ssl->conf->key_cert;
+
+    return( key_cert == NULL ? NULL : key_cert->key );
+}
+
+static inline mbedtls_x509_crt *mbedtls_ssl_own_cert( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_key_cert *key_cert;
+
+    if( ssl->handshake != NULL && ssl->handshake->key_cert != NULL )
+        key_cert = ssl->handshake->key_cert;
+    else
+        key_cert = ssl->conf->key_cert;
+
+    return( key_cert == NULL ? NULL : key_cert->cert );
+}
+
+/*
+ * Check usage of a certificate wrt extensions:
+ * keyUsage, extendedKeyUsage (later), and nSCertType (later).
+ *
+ * Warning: cert_endpoint is the endpoint of the cert (ie, of our peer when we
+ * check a cert we received from them)!
+ *
+ * Return 0 if everything is OK, -1 if not.
+ */
+int mbedtls_ssl_check_cert_usage( const mbedtls_x509_crt *cert,
+                          const mbedtls_ssl_ciphersuite_t *ciphersuite,
+                          int cert_endpoint,
+                          uint32_t *flags );
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
+
+void mbedtls_ssl_write_version( int major, int minor, int transport,
+                        unsigned char ver[2] );
+void mbedtls_ssl_read_version( int *major, int *minor, int transport,
+                       const unsigned char ver[2] );
+
+static inline size_t mbedtls_ssl_hdr_len( const mbedtls_ssl_context *ssl )
+{
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+        return( 13 );
+#else
+    ((void) ssl);
+#endif
+    return( 5 );
+}
+
+static inline size_t mbedtls_ssl_hs_hdr_len( const mbedtls_ssl_context *ssl )
+{
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+        return( 12 );
+#else
+    ((void) ssl);
+#endif
+    return( 4 );
+}
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+void mbedtls_ssl_send_flight_completed( mbedtls_ssl_context *ssl );
+void mbedtls_ssl_recv_flight_completed( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_resend( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_flight_transmit( mbedtls_ssl_context *ssl );
+#endif
+
+/* Visible for testing purposes only */
+#if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY)
+int mbedtls_ssl_dtls_replay_check( mbedtls_ssl_context *ssl );
+void mbedtls_ssl_dtls_replay_update( mbedtls_ssl_context *ssl );
+#endif
+
+int mbedtls_ssl_session_copy( mbedtls_ssl_session *dst,
+                              const mbedtls_ssl_session *src );
+
+/* constant-time buffer comparison */
+static inline int mbedtls_ssl_safer_memcmp( const void *a, const void *b, size_t n )
+{
+    size_t i;
+    volatile const unsigned char *A = (volatile const unsigned char *) a;
+    volatile const unsigned char *B = (volatile const unsigned char *) b;
+    volatile unsigned char diff = 0;
+
+    for( i = 0; i < n; i++ )
+    {
+        /* Read volatile data in order before computing diff.
+         * This avoids IAR compiler warning:
+         * 'the order of volatile accesses is undefined ..' */
+        unsigned char x = A[i], y = B[i];
+        diff |= x ^ y;
+    }
+
+    return( diff );
+}
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) || \
+    defined(MBEDTLS_SSL_PROTO_TLS1_1)
+int mbedtls_ssl_get_key_exchange_md_ssl_tls( mbedtls_ssl_context *ssl,
+                                        unsigned char *output,
+                                        unsigned char *data, size_t data_len );
+#endif /* MBEDTLS_SSL_PROTO_SSL3 || MBEDTLS_SSL_PROTO_TLS1 || \
+          MBEDTLS_SSL_PROTO_TLS1_1 */
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
+    defined(MBEDTLS_SSL_PROTO_TLS1_2)
+/* The hash buffer must have at least MBEDTLS_MD_MAX_SIZE bytes of length. */
+int mbedtls_ssl_get_key_exchange_md_tls1_2( mbedtls_ssl_context *ssl,
+                                            unsigned char *hash, size_t *hashlen,
+                                            unsigned char *data, size_t data_len,
+                                            mbedtls_md_type_t md_alg );
+#endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 || \
+          MBEDTLS_SSL_PROTO_TLS1_2 */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ssl_internal.h */