diff --git a/ChangeLog b/ChangeLog
index 3e5dd6808..c94218e74 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -104,6 +104,11 @@ Changes
      by Jiayuan Chen in #1377. Fixes #1437.
    * Improve security of RSA key generation by including criteria from FIPS
      186-4. Contributed by Jethro Beekman. #1380
+   * Declare functions in header files even when an alternative implementation
+     of the corresponding module is activated by defining the corresponding
+     MBEDTLS_XXX_ALT macro. This means that alternative implementations do
+     not need to copy the declarations, and ensures that they will have the
+     same API.
 
 = mbed TLS 2.8.0 branch released 2018-03-16
 
diff --git a/include/mbedtls/aes.h b/include/mbedtls/aes.h
index 3c5b1336b..e0fc238d7 100644
--- a/include/mbedtls/aes.h
+++ b/include/mbedtls/aes.h
@@ -62,14 +62,14 @@
 #define inline __inline
 #endif
 
-#if !defined(MBEDTLS_AES_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_AES_ALT)
+// Regular implementation
+//
+
 /**
  * \brief The AES context-type definition.
  */
@@ -88,6 +88,10 @@ typedef struct
 }
 mbedtls_aes_context;
 
+#else  /* MBEDTLS_AES_ALT */
+#include "aes_alt.h"
+#endif /* MBEDTLS_AES_ALT */
+
 /**
  * \brief          This function initializes the specified AES context.
  *
@@ -396,18 +400,6 @@ MBEDTLS_DEPRECATED void mbedtls_aes_decrypt( mbedtls_aes_context *ctx,
 #undef MBEDTLS_DEPRECATED
 #endif /* !MBEDTLS_DEPRECATED_REMOVED */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_AES_ALT */
-#include "aes_alt.h"
-#endif /* MBEDTLS_AES_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Checkup routine.
  *
diff --git a/include/mbedtls/arc4.h b/include/mbedtls/arc4.h
index f9d93f822..f11fc5be0 100644
--- a/include/mbedtls/arc4.h
+++ b/include/mbedtls/arc4.h
@@ -38,14 +38,14 @@
 
 #define MBEDTLS_ERR_ARC4_HW_ACCEL_FAILED                  -0x0019  /**< ARC4 hardware accelerator failed. */
 
-#if !defined(MBEDTLS_ARC4_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_ARC4_ALT)
+// Regular implementation
+//
+
 /**
  * \brief     ARC4 context structure
  *
@@ -61,6 +61,10 @@ typedef struct
 }
 mbedtls_arc4_context;
 
+#else  /* MBEDTLS_ARC4_ALT */
+#include "arc4_alt.h"
+#endif /* MBEDTLS_ARC4_ALT */
+
 /**
  * \brief          Initialize ARC4 context
  *
@@ -118,18 +122,6 @@ void mbedtls_arc4_setup( mbedtls_arc4_context *ctx, const unsigned char *key,
 int mbedtls_arc4_crypt( mbedtls_arc4_context *ctx, size_t length, const unsigned char *input,
                 unsigned char *output );
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_ARC4_ALT */
-#include "arc4_alt.h"
-#endif /* MBEDTLS_ARC4_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Checkup routine
  *
diff --git a/include/mbedtls/blowfish.h b/include/mbedtls/blowfish.h
index c0ef5a04c..22479be5a 100644
--- a/include/mbedtls/blowfish.h
+++ b/include/mbedtls/blowfish.h
@@ -44,14 +44,14 @@
 #define MBEDTLS_ERR_BLOWFISH_HW_ACCEL_FAILED                   -0x0017  /**< Blowfish hardware accelerator failed. */
 #define MBEDTLS_ERR_BLOWFISH_INVALID_INPUT_LENGTH              -0x0018  /**< Invalid data input length. */
 
-#if !defined(MBEDTLS_BLOWFISH_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_BLOWFISH_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          Blowfish context structure
  */
@@ -62,6 +62,10 @@ typedef struct
 }
 mbedtls_blowfish_context;
 
+#else  /* MBEDTLS_BLOWFISH_ALT */
+#include "blowfish_alt.h"
+#endif /* MBEDTLS_BLOWFISH_ALT */
+
 /**
  * \brief          Initialize Blowfish context
  *
@@ -198,8 +202,4 @@ int mbedtls_blowfish_crypt_ctr( mbedtls_blowfish_context *ctx,
 }
 #endif
 
-#else  /* MBEDTLS_BLOWFISH_ALT */
-#include "blowfish_alt.h"
-#endif /* MBEDTLS_BLOWFISH_ALT */
-
 #endif /* blowfish.h */
diff --git a/include/mbedtls/camellia.h b/include/mbedtls/camellia.h
index cf07629d9..f0466bfd7 100644
--- a/include/mbedtls/camellia.h
+++ b/include/mbedtls/camellia.h
@@ -40,14 +40,14 @@
 #define MBEDTLS_ERR_CAMELLIA_INVALID_INPUT_LENGTH         -0x0026  /**< Invalid data input length. */
 #define MBEDTLS_ERR_CAMELLIA_HW_ACCEL_FAILED              -0x0027  /**< Camellia hardware accelerator failed. */
 
-#if !defined(MBEDTLS_CAMELLIA_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_CAMELLIA_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          CAMELLIA context structure
  */
@@ -58,6 +58,10 @@ typedef struct
 }
 mbedtls_camellia_context;
 
+#else  /* MBEDTLS_CAMELLIA_ALT */
+#include "camellia_alt.h"
+#endif /* MBEDTLS_CAMELLIA_ALT */
+
 /**
  * \brief          Initialize CAMELLIA context
  *
@@ -211,18 +215,6 @@ int mbedtls_camellia_crypt_ctr( mbedtls_camellia_context *ctx,
                        unsigned char *output );
 #endif /* MBEDTLS_CIPHER_MODE_CTR */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_CAMELLIA_ALT */
-#include "camellia_alt.h"
-#endif /* MBEDTLS_CAMELLIA_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Checkup routine
  *
diff --git a/include/mbedtls/ccm.h b/include/mbedtls/ccm.h
index 630b7fdf6..48f73edda 100644
--- a/include/mbedtls/ccm.h
+++ b/include/mbedtls/ccm.h
@@ -40,14 +40,15 @@
 #define MBEDTLS_ERR_CCM_AUTH_FAILED     -0x000F /**< Authenticated decryption failed. */
 #define MBEDTLS_ERR_CCM_HW_ACCEL_FAILED -0x0011 /**< CCM hardware accelerator failed. */
 
-#if !defined(MBEDTLS_CCM_ALT)
-// Regular implementation
-//
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_CCM_ALT)
+// Regular implementation
+//
+
 /**
  * \brief    The CCM context-type definition. The CCM context is passed
  *           to the APIs called.
@@ -57,6 +58,10 @@ typedef struct {
 }
 mbedtls_ccm_context;
 
+#else  /* MBEDTLS_CCM_ALT */
+#include "ccm_alt.h"
+#endif /* MBEDTLS_CCM_ALT */
+
 /**
  * \brief           This function initializes the specified CCM context,
  *                  to make references valid, and prepare the context
@@ -148,17 +153,6 @@ int mbedtls_ccm_auth_decrypt( mbedtls_ccm_context *ctx, size_t length,
                       const unsigned char *input, unsigned char *output,
                       const unsigned char *tag, size_t tag_len );
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_CCM_ALT */
-#include "ccm_alt.h"
-#endif /* MBEDTLS_CCM_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
 
 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
 /**
diff --git a/include/mbedtls/cmac.h b/include/mbedtls/cmac.h
index 0ada7421b..913c05f8a 100644
--- a/include/mbedtls/cmac.h
+++ b/include/mbedtls/cmac.h
@@ -63,6 +63,10 @@ struct mbedtls_cmac_context_t
     size_t              unprocessed_len;
 };
 
+#else  /* !MBEDTLS_CMAC_ALT */
+#include "cmac_alt.h"
+#endif /* !MBEDTLS_CMAC_ALT */
+
 /**
  * \brief               This function sets the CMAC key, and prepares to authenticate
  *                      the input data.
@@ -185,18 +189,6 @@ int mbedtls_aes_cmac_prf_128( const unsigned char *key, size_t key_len,
                               unsigned char output[16] );
 #endif /* MBEDTLS_AES_C */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* !MBEDTLS_CMAC_ALT */
-#include "cmac_alt.h"
-#endif /* !MBEDTLS_CMAC_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #if defined(MBEDTLS_SELF_TEST) && ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_DES_C) )
 /**
  * \brief          The CMAC checkup routine.
diff --git a/include/mbedtls/des.h b/include/mbedtls/des.h
index 5a1a63652..6eb7d03ba 100644
--- a/include/mbedtls/des.h
+++ b/include/mbedtls/des.h
@@ -46,14 +46,14 @@
 
 #define MBEDTLS_DES_KEY_SIZE    8
 
-#if !defined(MBEDTLS_DES_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_DES_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          DES context structure
  *
@@ -76,6 +76,10 @@ typedef struct
 }
 mbedtls_des3_context;
 
+#else  /* MBEDTLS_DES_ALT */
+#include "des_alt.h"
+#endif /* MBEDTLS_DES_ALT */
+
 /**
  * \brief          Initialize DES context
  *
@@ -331,17 +335,6 @@ int mbedtls_des3_crypt_cbc( mbedtls_des3_context *ctx,
  */
 void mbedtls_des_setkey( uint32_t SK[32],
                          const unsigned char key[MBEDTLS_DES_KEY_SIZE] );
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_DES_ALT */
-#include "des_alt.h"
-#endif /* MBEDTLS_DES_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
 
 /**
  * \brief          Checkup routine
diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h
index 00fafd8d1..1bf572abe 100644
--- a/include/mbedtls/dhm.h
+++ b/include/mbedtls/dhm.h
@@ -65,7 +65,6 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 #include "bignum.h"
-#if !defined(MBEDTLS_DHM_ALT)
 
 /*
  * DHM Error codes
@@ -86,6 +85,8 @@
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_DHM_ALT)
+
 /**
  * \brief          The DHM context structure.
  */
@@ -105,6 +106,10 @@ typedef struct
 }
 mbedtls_dhm_context;
 
+#else /* MBEDTLS_DHM_ALT */
+#include "dhm_alt.h"
+#endif /* MBEDTLS_DHM_ALT */
+
 /**
  * \brief          This function initializes the DHM context.
  *
@@ -282,18 +287,6 @@ int mbedtls_dhm_parse_dhmfile( mbedtls_dhm_context *dhm, const char *path );
 #endif /* MBEDTLS_FS_IO */
 #endif /* MBEDTLS_ASN1_PARSE_C */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else /* MBEDTLS_DHM_ALT */
-#include "dhm_alt.h"
-#endif /* MBEDTLS_DHM_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          The DMH checkup routine.
  *
diff --git a/include/mbedtls/ecjpake.h b/include/mbedtls/ecjpake.h
index d86e8207f..cc2b316f5 100644
--- a/include/mbedtls/ecjpake.h
+++ b/include/mbedtls/ecjpake.h
@@ -44,8 +44,6 @@
 #include "ecp.h"
 #include "md.h"
 
-#if !defined(MBEDTLS_ECJPAKE_ALT)
-
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -58,6 +56,7 @@ typedef enum {
     MBEDTLS_ECJPAKE_SERVER,             /**< Server                         */
 } mbedtls_ecjpake_role;
 
+#if !defined(MBEDTLS_ECJPAKE_ALT)
 /**
  * EC J-PAKE context structure.
  *
@@ -88,6 +87,10 @@ typedef struct
     mbedtls_mpi s;                      /**< Pre-shared secret (passphrase) */
 } mbedtls_ecjpake_context;
 
+#else  /* MBEDTLS_ECJPAKE_ALT */
+#include "ecjpake_alt.h"
+#endif /* MBEDTLS_ECJPAKE_ALT */
+
 /**
  * \brief           Initialize a context
  *                  (just makes it ready for setup() or free()).
@@ -225,20 +228,10 @@ int mbedtls_ecjpake_derive_secret( mbedtls_ecjpake_context *ctx,
  */
 void mbedtls_ecjpake_free( mbedtls_ecjpake_context *ctx );
 
-#ifdef __cplusplus
-}
-#endif
 
-#else  /* MBEDTLS_ECJPAKE_ALT */
-#include "ecjpake_alt.h"
-#endif /* MBEDTLS_ECJPAKE_ALT */
 
 #if defined(MBEDTLS_SELF_TEST)
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Checkup routine
  *
@@ -246,10 +239,11 @@ extern "C" {
  */
 int mbedtls_ecjpake_self_test( int verbose );
 
+#endif /* MBEDTLS_SELF_TEST */
+
 #ifdef __cplusplus
 }
 #endif
 
-#endif /* MBEDTLS_SELF_TEST */
 
 #endif /* ecjpake.h */
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index e024da864..e063e4f68 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -39,15 +39,6 @@
 #define MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH                  -0x4C00  /**< The buffer contains a valid signature followed by more data. */
 #define MBEDTLS_ERR_ECP_HW_ACCEL_FAILED                   -0x4B80  /**< ECP hardware accelerator failed. */
 
-#if !defined(MBEDTLS_ECP_ALT)
-/*
- * default mbed TLS elliptic curve arithmetic implementation
- *
- * (in case MBEDTLS_ECP_ALT is defined then the developer has to provide an
- * alternative implementation for the whole module and it will replace this
- * one.)
- */
-
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -114,6 +105,15 @@ typedef struct
 }
 mbedtls_ecp_point;
 
+#if !defined(MBEDTLS_ECP_ALT)
+/*
+ * default mbed TLS elliptic curve arithmetic implementation
+ *
+ * (in case MBEDTLS_ECP_ALT is defined then the developer has to provide an
+ * alternative implementation for the whole module and it will replace this
+ * one.)
+ */
+
 /**
  * \brief           ECP group structure
  *
@@ -158,21 +158,6 @@ typedef struct
 }
 mbedtls_ecp_group;
 
-/**
- * \brief           ECP key pair structure
- *
- * A generic key pair that could be used for ECDSA, fixed ECDH, etc.
- *
- * \note Members purposefully in the same order as struc mbedtls_ecdsa_context.
- */
-typedef struct
-{
-    mbedtls_ecp_group grp;      /*!<  Elliptic curve and base point     */
-    mbedtls_mpi d;              /*!<  our secret value                  */
-    mbedtls_ecp_point Q;        /*!<  our public value                  */
-}
-mbedtls_ecp_keypair;
-
 /**
  * \name SECTION: Module settings
  *
@@ -232,6 +217,25 @@ mbedtls_ecp_keypair;
 
 /* \} name SECTION: Module settings */
 
+#else  /* MBEDTLS_ECP_ALT */
+#include "ecp_alt.h"
+#endif /* MBEDTLS_ECP_ALT */
+
+/**
+ * \brief           ECP key pair structure
+ *
+ * A generic key pair that could be used for ECDSA, fixed ECDH, etc.
+ *
+ * \note Members purposefully in the same order as struc mbedtls_ecdsa_context.
+ */
+typedef struct
+{
+    mbedtls_ecp_group grp;      /*!<  Elliptic curve and base point     */
+    mbedtls_mpi d;              /*!<  our secret value                  */
+    mbedtls_ecp_point Q;        /*!<  our public value                  */
+}
+mbedtls_ecp_keypair;
+
 /*
  * Point formats, from RFC 4492's enum ECPointFormat
  */
@@ -680,8 +684,4 @@ int mbedtls_ecp_self_test( int verbose );
 }
 #endif
 
-#else  /* MBEDTLS_ECP_ALT */
-#include "ecp_alt.h"
-#endif /* MBEDTLS_ECP_ALT */
-
 #endif /* ecp.h */
diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index 1e5a507a2..c2965e977 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -42,12 +42,12 @@
 #define MBEDTLS_ERR_GCM_HW_ACCEL_FAILED                   -0x0013  /**< GCM hardware accelerator failed. */
 #define MBEDTLS_ERR_GCM_BAD_INPUT                         -0x0014  /**< Bad input parameters to function. */
 
-#if !defined(MBEDTLS_GCM_ALT)
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_GCM_ALT)
+
 /**
  * \brief          The GCM context structure.
  */
@@ -66,6 +66,10 @@ typedef struct {
 }
 mbedtls_gcm_context;
 
+#else  /* !MBEDTLS_GCM_ALT */
+#include "gcm_alt.h"
+#endif /* !MBEDTLS_GCM_ALT */
+
 /**
  * \brief           This function initializes the specified GCM context,
  *                  to make references valid, and prepares the context
@@ -236,18 +240,6 @@ int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
  */
 void mbedtls_gcm_free( mbedtls_gcm_context *ctx );
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* !MBEDTLS_GCM_ALT */
-#include "gcm_alt.h"
-#endif /* !MBEDTLS_GCM_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          The GCM checkup routine.
  *
diff --git a/include/mbedtls/md2.h b/include/mbedtls/md2.h
index 0fd8b5afc..08e75b247 100644
--- a/include/mbedtls/md2.h
+++ b/include/mbedtls/md2.h
@@ -39,14 +39,14 @@
 
 #define MBEDTLS_ERR_MD2_HW_ACCEL_FAILED                   -0x002B  /**< MD2 hardware accelerator failed */
 
-#if !defined(MBEDTLS_MD2_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_MD2_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          MD2 context structure
  *
@@ -64,6 +64,10 @@ typedef struct
 }
 mbedtls_md2_context;
 
+#else  /* MBEDTLS_MD2_ALT */
+#include "md2_alt.h"
+#endif /* MBEDTLS_MD2_ALT */
+
 /**
  * \brief          Initialize MD2 context
  *
@@ -235,18 +239,6 @@ MBEDTLS_DEPRECATED void mbedtls_md2_process( mbedtls_md2_context *ctx );
 #undef MBEDTLS_DEPRECATED
 #endif /* !MBEDTLS_DEPRECATED_REMOVED */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_MD2_ALT */
-#include "md2_alt.h"
-#endif /* MBEDTLS_MD2_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Output = MD2( input buffer )
  *
diff --git a/include/mbedtls/md4.h b/include/mbedtls/md4.h
index 23fa95e46..8ee4e5cab 100644
--- a/include/mbedtls/md4.h
+++ b/include/mbedtls/md4.h
@@ -40,14 +40,14 @@
 
 #define MBEDTLS_ERR_MD4_HW_ACCEL_FAILED                   -0x002D  /**< MD4 hardware accelerator failed */
 
-#if !defined(MBEDTLS_MD4_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_MD4_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          MD4 context structure
  *
@@ -64,6 +64,10 @@ typedef struct
 }
 mbedtls_md4_context;
 
+#else  /* MBEDTLS_MD4_ALT */
+#include "md4_alt.h"
+#endif /* MBEDTLS_MD4_ALT */
+
 /**
  * \brief          Initialize MD4 context
  *
@@ -238,18 +242,6 @@ MBEDTLS_DEPRECATED void mbedtls_md4_process( mbedtls_md4_context *ctx,
 #undef MBEDTLS_DEPRECATED
 #endif /* !MBEDTLS_DEPRECATED_REMOVED */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_MD4_ALT */
-#include "md4_alt.h"
-#endif /* MBEDTLS_MD4_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Output = MD4( input buffer )
  *
diff --git a/include/mbedtls/md5.h b/include/mbedtls/md5.h
index 06ea4c5d4..43ead4b74 100644
--- a/include/mbedtls/md5.h
+++ b/include/mbedtls/md5.h
@@ -39,14 +39,14 @@
 
 #define MBEDTLS_ERR_MD5_HW_ACCEL_FAILED                   -0x002F  /**< MD5 hardware accelerator failed */
 
-#if !defined(MBEDTLS_MD5_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_MD5_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          MD5 context structure
  *
@@ -63,6 +63,10 @@ typedef struct
 }
 mbedtls_md5_context;
 
+#else  /* MBEDTLS_MD5_ALT */
+#include "md5_alt.h"
+#endif /* MBEDTLS_MD5_ALT */
+
 /**
  * \brief          Initialize MD5 context
  *
@@ -238,18 +242,6 @@ MBEDTLS_DEPRECATED void mbedtls_md5_process( mbedtls_md5_context *ctx,
 #undef MBEDTLS_DEPRECATED
 #endif /* !MBEDTLS_DEPRECATED_REMOVED */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_MD5_ALT */
-#include "md5_alt.h"
-#endif /* MBEDTLS_MD5_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Output = MD5( input buffer )
  *
diff --git a/include/mbedtls/ripemd160.h b/include/mbedtls/ripemd160.h
index 3a8b50a62..a0dac0c36 100644
--- a/include/mbedtls/ripemd160.h
+++ b/include/mbedtls/ripemd160.h
@@ -35,14 +35,14 @@
 
 #define MBEDTLS_ERR_RIPEMD160_HW_ACCEL_FAILED             -0x0031  /**< RIPEMD160 hardware accelerator failed */
 
-#if !defined(MBEDTLS_RIPEMD160_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_RIPEMD160_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          RIPEMD-160 context structure
  */
@@ -54,6 +54,10 @@ typedef struct
 }
 mbedtls_ripemd160_context;
 
+#else  /* MBEDTLS_RIPEMD160_ALT */
+#include "ripemd160.h"
+#endif /* MBEDTLS_RIPEMD160_ALT */
+
 /**
  * \brief          Initialize RIPEMD-160 context
  *
@@ -178,18 +182,6 @@ MBEDTLS_DEPRECATED void mbedtls_ripemd160_process(
 #undef MBEDTLS_DEPRECATED
 #endif /* !MBEDTLS_DEPRECATED_REMOVED */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_RIPEMD160_ALT */
-#include "ripemd160_alt.h"
-#endif /* MBEDTLS_RIPEMD160_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Output = RIPEMD-160( input buffer )
  *
diff --git a/include/mbedtls/rsa.h b/include/mbedtls/rsa.h
index f8b896592..df6e3e557 100644
--- a/include/mbedtls/rsa.h
+++ b/include/mbedtls/rsa.h
@@ -77,14 +77,14 @@
  * eg for alternative (PKCS#11) RSA implemenations in the PK layers.
  */
 
-#if !defined(MBEDTLS_RSA_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_RSA_ALT)
+// Regular implementation
+//
+
 /**
  * \brief   The RSA context structure.
  *
@@ -129,6 +129,10 @@ typedef struct
 }
 mbedtls_rsa_context;
 
+#else  /* MBEDTLS_RSA_ALT */
+#include "rsa_alt.h"
+#endif /* MBEDTLS_RSA_ALT */
+
 /**
  * \brief          This function initializes an RSA context.
  *
@@ -1112,18 +1116,6 @@ int mbedtls_rsa_copy( mbedtls_rsa_context *dst, const mbedtls_rsa_context *src )
  */
 void mbedtls_rsa_free( mbedtls_rsa_context *ctx );
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_RSA_ALT */
-#include "rsa_alt.h"
-#endif /* MBEDTLS_RSA_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          The RSA checkup routine.
  *
diff --git a/include/mbedtls/sha1.h b/include/mbedtls/sha1.h
index eec3f95bc..8f805fb42 100644
--- a/include/mbedtls/sha1.h
+++ b/include/mbedtls/sha1.h
@@ -42,14 +42,14 @@
 
 #define MBEDTLS_ERR_SHA1_HW_ACCEL_FAILED                  -0x0035  /**< SHA-1 hardware accelerator failed */
 
-#if !defined(MBEDTLS_SHA1_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_SHA1_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          The SHA-1 context structure.
  *
@@ -66,6 +66,10 @@ typedef struct
 }
 mbedtls_sha1_context;
 
+#else  /* MBEDTLS_SHA1_ALT */
+#include "sha1_alt.h"
+#endif /* MBEDTLS_SHA1_ALT */
+
 /**
  * \brief          This function initializes a SHA-1 context.
  *
@@ -243,18 +247,6 @@ MBEDTLS_DEPRECATED void mbedtls_sha1_process( mbedtls_sha1_context *ctx,
 #undef MBEDTLS_DEPRECATED
 #endif /* !MBEDTLS_DEPRECATED_REMOVED */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_SHA1_ALT */
-#include "sha1_alt.h"
-#endif /* MBEDTLS_SHA1_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          This function calculates the SHA-1 checksum of a buffer.
  *
diff --git a/include/mbedtls/sha256.h b/include/mbedtls/sha256.h
index c4465e586..adf31a82e 100644
--- a/include/mbedtls/sha256.h
+++ b/include/mbedtls/sha256.h
@@ -38,14 +38,14 @@
 
 #define MBEDTLS_ERR_SHA256_HW_ACCEL_FAILED                -0x0037  /**< SHA-256 hardware accelerator failed */
 
-#if !defined(MBEDTLS_SHA256_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_SHA256_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          The SHA-256 context structure.
  *
@@ -63,6 +63,10 @@ typedef struct
 }
 mbedtls_sha256_context;
 
+#else  /* MBEDTLS_SHA256_ALT */
+#include "sha256_alt.h"
+#endif /* MBEDTLS_SHA256_ALT */
+
 /**
  * \brief          This function initializes a SHA-256 context.
  *
@@ -198,17 +202,6 @@ MBEDTLS_DEPRECATED void mbedtls_sha256_process( mbedtls_sha256_context *ctx,
 
 #undef MBEDTLS_DEPRECATED
 #endif /* !MBEDTLS_DEPRECATED_REMOVED */
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_SHA256_ALT */
-#include "sha256_alt.h"
-#endif /* MBEDTLS_SHA256_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
 
 /**
  * \brief          This function calculates the SHA-224 or SHA-256
diff --git a/include/mbedtls/sha512.h b/include/mbedtls/sha512.h
index ee88fcf31..5bb83f43b 100644
--- a/include/mbedtls/sha512.h
+++ b/include/mbedtls/sha512.h
@@ -37,14 +37,14 @@
 
 #define MBEDTLS_ERR_SHA512_HW_ACCEL_FAILED                -0x0039  /**< SHA-512 hardware accelerator failed */
 
-#if !defined(MBEDTLS_SHA512_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_SHA512_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          The SHA-512 context structure.
  *
@@ -62,6 +62,10 @@ typedef struct
 }
 mbedtls_sha512_context;
 
+#else  /* MBEDTLS_SHA512_ALT */
+#include "sha512_alt.h"
+#endif /* MBEDTLS_SHA512_ALT */
+
 /**
  * \brief          This function initializes a SHA-512 context.
  *
@@ -197,18 +201,6 @@ MBEDTLS_DEPRECATED void mbedtls_sha512_process(
 #undef MBEDTLS_DEPRECATED
 #endif /* !MBEDTLS_DEPRECATED_REMOVED */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_SHA512_ALT */
-#include "sha512_alt.h"
-#endif /* MBEDTLS_SHA512_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          This function calculates the SHA-512 or SHA-384
  *                 checksum of a buffer.
diff --git a/include/mbedtls/timing.h b/include/mbedtls/timing.h
index 2c497bf4e..bbcb90688 100644
--- a/include/mbedtls/timing.h
+++ b/include/mbedtls/timing.h
@@ -30,16 +30,16 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 
-#if !defined(MBEDTLS_TIMING_ALT)
-// Regular implementation
-//
-
 #include <stdint.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_TIMING_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          timer structure
  */
@@ -58,6 +58,10 @@ typedef struct
     uint32_t                        fin_ms;
 } mbedtls_timing_delay_context;
 
+#else  /* MBEDTLS_TIMING_ALT */
+#include "timing_alt.h"
+#endif /* MBEDTLS_TIMING_ALT */
+
 extern volatile int mbedtls_timing_alarmed;
 
 /**
@@ -133,18 +137,6 @@ void mbedtls_timing_set_delay( void *data, uint32_t int_ms, uint32_t fin_ms );
  */
 int mbedtls_timing_get_delay( void *data );
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_TIMING_ALT */
-#include "timing_alt.h"
-#endif /* MBEDTLS_TIMING_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #if defined(MBEDTLS_SELF_TEST)
 /**
  * \brief          Checkup routine
diff --git a/include/mbedtls/xtea.h b/include/mbedtls/xtea.h
index 34ccee3c2..8df708a3a 100644
--- a/include/mbedtls/xtea.h
+++ b/include/mbedtls/xtea.h
@@ -39,14 +39,14 @@
 #define MBEDTLS_ERR_XTEA_INVALID_INPUT_LENGTH             -0x0028  /**< The data input has an invalid length. */
 #define MBEDTLS_ERR_XTEA_HW_ACCEL_FAILED                  -0x0029  /**< XTEA hardware accelerator failed. */
 
-#if !defined(MBEDTLS_XTEA_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_XTEA_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          XTEA context structure
  */
@@ -56,6 +56,10 @@ typedef struct
 }
 mbedtls_xtea_context;
 
+#else  /* MBEDTLS_XTEA_ALT */
+#include "xtea_alt.h"
+#endif /* MBEDTLS_XTEA_ALT */
+
 /**
  * \brief          Initialize XTEA context
  *
@@ -115,18 +119,6 @@ int mbedtls_xtea_crypt_cbc( mbedtls_xtea_context *ctx,
                     unsigned char *output);
 #endif /* MBEDTLS_CIPHER_MODE_CBC */
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_XTEA_ALT */
-#include "xtea_alt.h"
-#endif /* MBEDTLS_XTEA_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief          Checkup routine
  *