diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index df3a03c..91950f9 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -197,23 +197,35 @@
 const mbedtls_pk_info_t *mbedtls_pk_info_from_type( mbedtls_pk_type_t pk_type );
 
 /**
- * \brief           Initialize a mbedtls_pk_context (as NONE)
+ * \brief           Initialize a #mbedtls_pk_context (as NONE).
+ *
+ * \param ctx       The context to initialize.
+ *                  This must not be \c NULL.
  */
 void mbedtls_pk_init( mbedtls_pk_context *ctx );
 
 /**
- * \brief           Free a mbedtls_pk_context
+ * \brief           Free the components of a #mbedtls_pk_context.
+ *
+ * \param ctx       The context to clear. It must have been initialized.
+ *                  If this is \c NULL, this function does nothing.
  */
 void mbedtls_pk_free( mbedtls_pk_context *ctx );
 
 #if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
 /**
  * \brief           Initialize a restart context
+ *
+ * \param ctx       The context to initialize.
+ *                  This must not be \c NULL.
  */
 void mbedtls_pk_restart_init( mbedtls_pk_restart_ctx *ctx );
 
 /**
  * \brief           Free the components of a restart context
+ *
+ * \param ctx       The context to clear. It must have been initialized.
+ *                  If this is \c NULL, this function does nothing.
  */
 void mbedtls_pk_restart_free( mbedtls_pk_restart_ctx *ctx );
 #endif /* MBEDTLS_ECDSA_C && MBEDTLS_ECP_RESTARTABLE */
@@ -222,7 +234,8 @@
  * \brief           Initialize a PK context with the information given
  *                  and allocates the type-specific PK subcontext.
  *
- * \param ctx       Context to initialize. Must be empty (type NONE).
+ * \param ctx       Context to initialize. It must not have been set
+ *                  up yet (type #MBEDTLS_PK_NONE).
  * \param info      Information to use
  *
  * \return          0 on success,
@@ -238,7 +251,8 @@
 /**
  * \brief           Initialize an RSA-alt context
  *
- * \param ctx       Context to initialize. Must be empty (type NONE).
+ * \param ctx       Context to initialize. It must not have been set
+ *                  up yet (type #MBEDTLS_PK_NONE).
  * \param key       RSA key pointer
  * \param decrypt_func  Decryption function
  * \param sign_func     Signing function
@@ -258,7 +272,7 @@
 /**
  * \brief           Get the size in bits of the underlying key
  *
- * \param ctx       Context to use
+ * \param ctx       The context to query. It must have been initialized.
  *
  * \return          Key size in bits, or 0 on error
  */
@@ -266,7 +280,8 @@
 
 /**
  * \brief           Get the length in bytes of the underlying key
- * \param ctx       Context to use
+ *
+ * \param ctx       The context to query. It must have been initialized.
  *
  * \return          Key length in bytes, or 0 on error
  */
@@ -278,18 +293,21 @@
 /**
  * \brief           Tell if a context can do the operation given by type
  *
- * \param ctx       Context to test
- * \param type      Target type
+ * \param ctx       The context to query. It must have been initialized.
+ * \param type      The desired type.
  *
- * \return          0 if context can't do the operations,
- *                  1 otherwise.
+ * \return          1 if the context can do operations on the given type.
+ * \return          0 if the context cannot do the operations on the given
+ *                  type. This is always the case for a context that has
+ *                  been initialized but not set up, or that has been
+ *                  cleared with mbedtls_pk_free().
  */
 int mbedtls_pk_can_do( const mbedtls_pk_context *ctx, mbedtls_pk_type_t type );
 
 /**
  * \brief           Verify signature (including padding if relevant).
  *
- * \param ctx       PK context to use
+ * \param ctx       The PK context to use. It must have been set up.
  * \param md_alg    Hash algorithm used (see notes)
  * \param hash      Hash of the message to sign
  * \param hash_len  Hash length or 0 (see notes)
@@ -322,7 +340,7 @@
  *                  \c mbedtls_ecp_set_max_ops() to reduce blocking for ECC
  *                  operations. For RSA, same as \c mbedtls_pk_verify().
  *
- * \param ctx       PK context to use
+ * \param ctx       The PK context to use. It must have been set up.
  * \param md_alg    Hash algorithm used (see notes)
  * \param hash      Hash of the message to sign
  * \param hash_len  Hash length or 0 (see notes)
@@ -346,7 +364,7 @@
  *
  * \param type      Signature type (inc. possible padding type) to verify
  * \param options   Pointer to type-specific options, or NULL
- * \param ctx       PK context to use
+ * \param ctx       The PK context to use. It must have been set up.
  * \param md_alg    Hash algorithm used (see notes)
  * \param hash      Hash of the message to sign
  * \param hash_len  Hash length or 0 (see notes)
@@ -377,7 +395,8 @@
 /**
  * \brief           Make signature, including padding if relevant.
  *
- * \param ctx       PK context to use - must hold a private key
+ * \param ctx       The PK context to use. It must have been set up
+ *                  with a private key.
  * \param md_alg    Hash algorithm used (see notes)
  * \param hash      Hash of the message to sign
  * \param hash_len  Hash length or 0 (see notes)
@@ -411,7 +430,8 @@
  *                  \c mbedtls_ecp_set_max_ops() to reduce blocking for ECC
  *                  operations. For RSA, same as \c mbedtls_pk_sign().
  *
- * \param ctx       PK context to use - must hold a private key
+ * \param ctx       The PK context to use. It must have been set up
+ *                  with a private key.
  * \param md_alg    Hash algorithm used (see notes)
  * \param hash      Hash of the message to sign
  * \param hash_len  Hash length or 0 (see notes)
@@ -435,7 +455,8 @@
 /**
  * \brief           Decrypt message (including padding if relevant).
  *
- * \param ctx       PK context to use - must hold a private key
+ * \param ctx       The PK context to use. It must have been set up
+ *                  with a private key.
  * \param input     Input to decrypt
  * \param ilen      Input size
  * \param output    Decrypted output
@@ -456,7 +477,7 @@
 /**
  * \brief           Encrypt message (including padding if relevant).
  *
- * \param ctx       PK context to use
+ * \param ctx       The PK context to use. It must have been set up.
  * \param input     Message to encrypt
  * \param ilen      Message size
  * \param output    Encrypted output
@@ -487,7 +508,7 @@
 /**
  * \brief           Export debug information
  *
- * \param ctx       Context to use
+ * \param ctx       The PK context to use. It must have been initialized.
  * \param items     Place to write debug items
  *
  * \return          0 on success or MBEDTLS_ERR_PK_BAD_INPUT_DATA
@@ -497,7 +518,7 @@
 /**
  * \brief           Access the type name
  *
- * \param ctx       Context to use
+ * \param ctx       The PK context to use. It must have been initialized.
  *
  * \return          Type name on success, or "invalid PK"
  */
@@ -506,9 +527,10 @@
 /**
  * \brief           Get the key type
  *
- * \param ctx       Context to use
+ * \param ctx       The PK context to use. It must have been initialized.
  *
- * \return          Type on success, or MBEDTLS_PK_NONE
+ * \return          Type on success.
+ * \return          #MBEDTLS_PK_NONE for a context that has not been set up.
  */
 mbedtls_pk_type_t mbedtls_pk_get_type( const mbedtls_pk_context *ctx );
 
@@ -517,12 +539,22 @@
 /**
  * \brief           Parse a private key in PEM or DER format
  *
- * \param ctx       key to be initialized
- * \param key       input buffer
- * \param keylen    size of the buffer
- *                  (including the terminating null byte for PEM data)
- * \param pwd       password for decryption (optional)
- * \param pwdlen    size of the password
+ * \param ctx       The PK context to fill. It must have been initialized
+ *                  but not set up.
+ * \param key       Input buffer to parse.
+ *                  The buffer must contain the input exactly, with no
+ *                  extra trailing material. For PEM, the buffer must
+ *                  contain a null-terminated string.
+ * \param keylen    Size of \b key in bytes.
+ *                  For PEM data, this includes the terminating null byte,
+ *                  so \p keylen must be equal to `strlen(key) + 1`.
+ * \param pwd       Optional password for decryption.
+ *                  Pass \c NULL if expecting a non-encrypted key.
+ *                  Pass a string of \p pwdlen bytes if expecting an encrypted
+ *                  key; a non-encrypted key will also be accepted.
+ *                  The empty password is not supported.
+ * \param pwdlen    Size of the password in bytes.
+ *                  Ignored if \p pwd is \c NULL.
  *
  * \note            On entry, ctx must be empty, either freshly initialised
  *                  with mbedtls_pk_init() or reset with mbedtls_pk_free(). If you need a
@@ -540,10 +572,15 @@
 /**
  * \brief           Parse a public key in PEM or DER format
  *
- * \param ctx       key to be initialized
- * \param key       input buffer
- * \param keylen    size of the buffer
- *                  (including the terminating null byte for PEM data)
+ * \param ctx       The PK context to fill. It must have been initialized
+ *                  but not set up.
+ * \param key       Input buffer to parse.
+ *                  The buffer must contain the input exactly, with no
+ *                  extra trailing material. For PEM, the buffer must
+ *                  contain a null-terminated string.
+ * \param keylen    Size of \b key in bytes.
+ *                  For PEM data, this includes the terminating null byte,
+ *                  so \p keylen must be equal to `strlen(key) + 1`.
  *
  * \note            On entry, ctx must be empty, either freshly initialised
  *                  with mbedtls_pk_init() or reset with mbedtls_pk_free(). If you need a
@@ -561,9 +598,14 @@
 /**
  * \brief           Load and parse a private key
  *
- * \param ctx       key to be initialized
+ * \param ctx       The PK context to fill. It must have been initialized
+ *                  but not set up.
  * \param path      filename to read the private key from
- * \param password  password to decrypt the file (can be NULL)
+ * \param password  Optional password to decrypt the file.
+ *                  Pass \c NULL if expecting a non-encrypted key.
+ *                  Pass a null-terminated string if expecting an encrypted
+ *                  key; a non-encrypted key will also be accepted.
+ *                  The empty password is not supported.
  *
  * \note            On entry, ctx must be empty, either freshly initialised
  *                  with mbedtls_pk_init() or reset with mbedtls_pk_free(). If you need a
@@ -580,7 +622,8 @@
 /**
  * \brief           Load and parse a public key
  *
- * \param ctx       key to be initialized
+ * \param ctx       The PK context to fill. It must have been initialized
+ *                  but not set up.
  * \param path      filename to read the public key from
  *
  * \note            On entry, ctx must be empty, either freshly initialised
@@ -603,7 +646,7 @@
  *                        return value to determine where you should start
  *                        using the buffer
  *
- * \param ctx       private to write away
+ * \param ctx       PK context which must contain a valid private key.
  * \param buf       buffer to write to
  * \param size      size of the buffer
  *
@@ -618,7 +661,7 @@
  *                        return value to determine where you should start
  *                        using the buffer
  *
- * \param ctx       public key to write away
+ * \param ctx       PK context which must contain a valid public or private key.
  * \param buf       buffer to write to
  * \param size      size of the buffer
  *
@@ -631,9 +674,10 @@
 /**
  * \brief           Write a public key to a PEM string
  *
- * \param ctx       public key to write away
- * \param buf       buffer to write to
- * \param size      size of the buffer
+ * \param ctx       PK context which must contain a valid public or private key.
+ * \param buf       Buffer to write to. The output includes a
+ *                  terminating null byte.
+ * \param size      Size of the buffer in bytes.
  *
  * \return          0 if successful, or a specific error code
  */
@@ -642,9 +686,10 @@
 /**
  * \brief           Write a private key to a PKCS#1 or SEC1 PEM string
  *
- * \param ctx       private to write away
- * \param buf       buffer to write to
- * \param size      size of the buffer
+ * \param ctx       PK context which must contain a valid private key.
+ * \param buf       Buffer to write to. The output includes a
+ *                  terminating null byte.
+ * \param size      Size of the buffer in bytes.
  *
  * \return          0 if successful, or a specific error code
  */
@@ -663,7 +708,8 @@
  *
  * \param p         the position in the ASN.1 data
  * \param end       end of the buffer
- * \param pk        the key to fill
+ * \param pk        The PK context to fill. It must have been initialized
+ *                  but not set up.
  *
  * \return          0 if successful, or a specific PK error code
  */
@@ -678,7 +724,7 @@
  *
  * \param p         reference to current position pointer
  * \param start     start of the buffer (for bounds-checking)
- * \param key       public key to write away
+ * \param key       PK context which must contain a valid public or private key.
  *
  * \return          the length written or a negative error code
  */
diff --git a/library/pk.c b/library/pk.c
index e0e8dba..2658627 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -44,13 +44,18 @@
 #include <limits.h>
 #include <stdint.h>
 
+/* Parameter validation macros based on platform_util.h */
+#define PK_VALIDATE_RET( cond )    \
+    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_PK_BAD_INPUT_DATA )
+#define PK_VALIDATE( cond )        \
+    MBEDTLS_INTERNAL_VALIDATE( cond )
+
 /*
  * Initialise a mbedtls_pk_context
  */
 void mbedtls_pk_init( mbedtls_pk_context *ctx )
 {
-    if( ctx == NULL )
-        return;
+    PK_VALIDATE( ctx != NULL );
 
     ctx->pk_info = NULL;
     ctx->pk_ctx = NULL;
@@ -75,6 +80,7 @@
  */
 void mbedtls_pk_restart_init( mbedtls_pk_restart_ctx *ctx )
 {
+    PK_VALIDATE( ctx != NULL );
     ctx->pk_info = NULL;
     ctx->rs_ctx = NULL;
 }
@@ -128,7 +134,8 @@
  */
 int mbedtls_pk_setup( mbedtls_pk_context *ctx, const mbedtls_pk_info_t *info )
 {
-    if( ctx == NULL || info == NULL || ctx->pk_info != NULL )
+    PK_VALIDATE_RET( ctx != NULL );
+    if( info == NULL || ctx->pk_info != NULL )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
     if( ( ctx->pk_ctx = info->ctx_alloc_func() ) == NULL )
@@ -151,7 +158,8 @@
     mbedtls_rsa_alt_context *rsa_alt;
     const mbedtls_pk_info_t *info = &mbedtls_rsa_alt_info;
 
-    if( ctx == NULL || ctx->pk_info != NULL )
+    PK_VALIDATE_RET( ctx != NULL );
+    if( ctx->pk_info != NULL )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
     if( ( ctx->pk_ctx = info->ctx_alloc_func() ) == NULL )
@@ -175,7 +183,9 @@
  */
 int mbedtls_pk_can_do( const mbedtls_pk_context *ctx, mbedtls_pk_type_t type )
 {
-    /* null or NONE context can't do anything */
+    /* A context with null pk_info is not set up yet and can't do anything.
+     * For backward compatibility, also accept NULL instead of a context
+     * pointer. */
     if( ctx == NULL || ctx->pk_info == NULL )
         return( 0 );
 
@@ -232,7 +242,12 @@
                const unsigned char *sig, size_t sig_len,
                mbedtls_pk_restart_ctx *rs_ctx )
 {
-    if( ctx == NULL || ctx->pk_info == NULL ||
+    PK_VALIDATE_RET( ctx != NULL );
+    PK_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hash_len == 0 ) ||
+                     hash != NULL );
+    PK_VALIDATE_RET( sig != NULL );
+
+    if( ctx->pk_info == NULL ||
         pk_hashlen_helper( md_alg, &hash_len ) != 0 )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
@@ -285,7 +300,12 @@
                    const unsigned char *hash, size_t hash_len,
                    const unsigned char *sig, size_t sig_len )
 {
-    if( ctx == NULL || ctx->pk_info == NULL )
+    PK_VALIDATE_RET( ctx != NULL );
+    PK_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hash_len == 0 ) ||
+                     hash != NULL );
+    PK_VALIDATE_RET( sig != NULL );
+
+    if( ctx->pk_info == NULL )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
     if( ! mbedtls_pk_can_do( ctx, type ) )
@@ -345,7 +365,12 @@
              int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
              mbedtls_pk_restart_ctx *rs_ctx )
 {
-    if( ctx == NULL || ctx->pk_info == NULL ||
+    PK_VALIDATE_RET( ctx != NULL );
+    PK_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hash_len == 0 ) ||
+                     hash != NULL );
+    PK_VALIDATE_RET( sig != NULL );
+
+    if( ctx->pk_info == NULL ||
         pk_hashlen_helper( md_alg, &hash_len ) != 0 )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
@@ -399,7 +424,12 @@
                 unsigned char *output, size_t *olen, size_t osize,
                 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
 {
-    if( ctx == NULL || ctx->pk_info == NULL )
+    PK_VALIDATE_RET( ctx != NULL );
+    PK_VALIDATE_RET( input != NULL || ilen == 0 );
+    PK_VALIDATE_RET( output != NULL || osize == 0 );
+    PK_VALIDATE_RET( olen != NULL );
+
+    if( ctx->pk_info == NULL )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
     if( ctx->pk_info->decrypt_func == NULL )
@@ -417,7 +447,12 @@
                 unsigned char *output, size_t *olen, size_t osize,
                 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
 {
-    if( ctx == NULL || ctx->pk_info == NULL )
+    PK_VALIDATE_RET( ctx != NULL );
+    PK_VALIDATE_RET( input != NULL || ilen == 0 );
+    PK_VALIDATE_RET( output != NULL || osize == 0 );
+    PK_VALIDATE_RET( olen != NULL );
+
+    if( ctx->pk_info == NULL )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
     if( ctx->pk_info->encrypt_func == NULL )
@@ -432,8 +467,11 @@
  */
 int mbedtls_pk_check_pair( const mbedtls_pk_context *pub, const mbedtls_pk_context *prv )
 {
-    if( pub == NULL || pub->pk_info == NULL ||
-        prv == NULL || prv->pk_info == NULL ||
+    PK_VALIDATE_RET( pub != NULL );
+    PK_VALIDATE_RET( prv != NULL );
+
+    if( pub->pk_info == NULL ||
+        prv->pk_info == NULL ||
         prv->pk_info->check_pair_func == NULL )
     {
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
@@ -458,6 +496,8 @@
  */
 size_t mbedtls_pk_get_bitlen( const mbedtls_pk_context *ctx )
 {
+    /* For backward compatibility, accept NULL or a context that
+     * isn't set up yet, and return a fake value that should be safe. */
     if( ctx == NULL || ctx->pk_info == NULL )
         return( 0 );
 
@@ -469,7 +509,8 @@
  */
 int mbedtls_pk_debug( const mbedtls_pk_context *ctx, mbedtls_pk_debug_item *items )
 {
-    if( ctx == NULL || ctx->pk_info == NULL )
+    PK_VALIDATE_RET( ctx != NULL );
+    if( ctx->pk_info == NULL )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
     if( ctx->pk_info->debug_func == NULL )
diff --git a/library/pkparse.c b/library/pkparse.c
index 86d9fb0..ae210bc 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -61,6 +61,12 @@
 #define mbedtls_free       free
 #endif
 
+/* Parameter validation macros based on platform_util.h */
+#define PK_VALIDATE_RET( cond )    \
+    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_PK_BAD_INPUT_DATA )
+#define PK_VALIDATE( cond )        \
+    MBEDTLS_INTERNAL_VALIDATE( cond )
+
 #if defined(MBEDTLS_FS_IO)
 /*
  * Load all data from a file into a given buffer.
@@ -74,6 +80,10 @@
     FILE *f;
     long size;
 
+    PK_VALIDATE_RET( path != NULL );
+    PK_VALIDATE_RET( buf != NULL );
+    PK_VALIDATE_RET( n != NULL );
+
     if( ( f = fopen( path, "rb" ) ) == NULL )
         return( MBEDTLS_ERR_PK_FILE_IO_ERROR );
 
@@ -124,6 +134,9 @@
     size_t n;
     unsigned char *buf;
 
+    PK_VALIDATE_RET( ctx != NULL );
+    PK_VALIDATE_RET( path != NULL );
+
     if( ( ret = mbedtls_pk_load_file( path, &buf, &n ) ) != 0 )
         return( ret );
 
@@ -148,6 +161,9 @@
     size_t n;
     unsigned char *buf;
 
+    PK_VALIDATE_RET( ctx != NULL );
+    PK_VALIDATE_RET( path != NULL );
+
     if( ( ret = mbedtls_pk_load_file( path, &buf, &n ) ) != 0 )
         return( ret );
 
@@ -605,6 +621,11 @@
     mbedtls_pk_type_t pk_alg = MBEDTLS_PK_NONE;
     const mbedtls_pk_info_t *pk_info;
 
+    PK_VALIDATE_RET( p != NULL );
+    PK_VALIDATE_RET( *p != NULL );
+    PK_VALIDATE_RET( end != NULL );
+    PK_VALIDATE_RET( pk != NULL );
+
     if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
                     MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
     {
@@ -1145,16 +1166,22 @@
 {
     int ret;
     const mbedtls_pk_info_t *pk_info;
-
 #if defined(MBEDTLS_PEM_PARSE_C)
     size_t len;
     mbedtls_pem_context pem;
+#endif
 
-    mbedtls_pem_init( &pem );
+    PK_VALIDATE_RET( pk != NULL );
+    if( keylen == 0 )
+        return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
+    PK_VALIDATE_RET( key != NULL );
+
+#if defined(MBEDTLS_PEM_PARSE_C)
+   mbedtls_pem_init( &pem );
 
 #if defined(MBEDTLS_RSA_C)
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( keylen == 0 || key[keylen - 1] != '\0' )
+    if( key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1185,7 +1212,7 @@
 
 #if defined(MBEDTLS_ECP_C)
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( keylen == 0 || key[keylen - 1] != '\0' )
+    if( key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1215,7 +1242,7 @@
 #endif /* MBEDTLS_ECP_C */
 
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( keylen == 0 || key[keylen - 1] != '\0' )
+    if( key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1238,7 +1265,7 @@
 
 #if defined(MBEDTLS_PKCS12_C) || defined(MBEDTLS_PKCS5_C)
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( keylen == 0 || key[keylen - 1] != '\0' )
+    if( key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1276,9 +1303,6 @@
     {
         unsigned char *key_copy;
 
-        if( keylen == 0 )
-            return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
-
         if( ( key_copy = mbedtls_calloc( 1, keylen ) ) == NULL )
             return( MBEDTLS_ERR_PK_ALLOC_FAILED );
 
@@ -1360,11 +1384,18 @@
 #if defined(MBEDTLS_PEM_PARSE_C)
     size_t len;
     mbedtls_pem_context pem;
+#endif
 
+    PK_VALIDATE_RET( ctx != NULL );
+    if( keylen == 0 )
+        return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
+    PK_VALIDATE_RET( key != NULL || keylen == 0 );
+
+#if defined(MBEDTLS_PEM_PARSE_C)
     mbedtls_pem_init( &pem );
 #if defined(MBEDTLS_RSA_C)
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( keylen == 0 || key[keylen - 1] != '\0' )
+    if( key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1395,7 +1426,7 @@
 #endif /* MBEDTLS_RSA_C */
 
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( keylen == 0 || key[keylen - 1] != '\0' )
+    if( key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
diff --git a/library/pkwrite.c b/library/pkwrite.c
index 8eabd88..8d1da2f 100644
--- a/library/pkwrite.c
+++ b/library/pkwrite.c
@@ -30,6 +30,7 @@
 #include "mbedtls/pk.h"
 #include "mbedtls/asn1write.h"
 #include "mbedtls/oid.h"
+#include "mbedtls/platform_util.h"
 
 #include <string.h>
 
@@ -54,6 +55,12 @@
 #define mbedtls_free       free
 #endif
 
+/* Parameter validation macros based on platform_util.h */
+#define PK_VALIDATE_RET( cond )    \
+    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_PK_BAD_INPUT_DATA )
+#define PK_VALIDATE( cond )        \
+    MBEDTLS_INTERNAL_VALIDATE( cond )
+
 #if defined(MBEDTLS_RSA_C)
 /*
  *  RSAPublicKey ::= SEQUENCE {
@@ -151,6 +158,11 @@
     int ret;
     size_t len = 0;
 
+    PK_VALIDATE_RET( p != NULL );
+    PK_VALIDATE_RET( *p != NULL );
+    PK_VALIDATE_RET( start != NULL );
+    PK_VALIDATE_RET( key != NULL );
+
 #if defined(MBEDTLS_RSA_C)
     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
         MBEDTLS_ASN1_CHK_ADD( len, pk_write_rsa_pubkey( p, start, mbedtls_pk_rsa( *key ) ) );
@@ -173,6 +185,11 @@
     size_t len = 0, par_len = 0, oid_len;
     const char *oid;
 
+    PK_VALIDATE_RET( key != NULL );
+    if( size == 0 )
+        return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
+    PK_VALIDATE_RET( buf != NULL );
+
     c = buf + size;
 
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, key ) );
@@ -217,9 +234,16 @@
 int mbedtls_pk_write_key_der( mbedtls_pk_context *key, unsigned char *buf, size_t size )
 {
     int ret;
-    unsigned char *c = buf + size;
+    unsigned char *c;
     size_t len = 0;
 
+    PK_VALIDATE_RET( key != NULL );
+    if( size == 0 )
+        return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
+    PK_VALIDATE_RET( buf != NULL );
+
+    c = buf + size;
+
 #if defined(MBEDTLS_RSA_C)
     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
     {
@@ -457,6 +481,9 @@
     unsigned char output_buf[PUB_DER_MAX_BYTES];
     size_t olen = 0;
 
+    PK_VALIDATE_RET( key != NULL );
+    PK_VALIDATE_RET( buf != NULL || size == 0 );
+
     if( ( ret = mbedtls_pk_write_pubkey_der( key, output_buf,
                                      sizeof(output_buf) ) ) < 0 )
     {
@@ -480,6 +507,9 @@
     const char *begin, *end;
     size_t olen = 0;
 
+    PK_VALIDATE_RET( key != NULL );
+    PK_VALIDATE_RET( buf != NULL || size == 0 );
+
     if( ( ret = mbedtls_pk_write_key_der( key, output_buf, sizeof(output_buf) ) ) < 0 )
         return( ret );
 
diff --git a/tests/suites/test_suite_pk.data b/tests/suites/test_suite_pk.data
index 478cde7..e41dfa7 100644
--- a/tests/suites/test_suite_pk.data
+++ b/tests/suites/test_suite_pk.data
@@ -1,3 +1,13 @@
+PK invalid parameters
+invalid_parameters:
+
+PK valid parameters
+valid_parameters:
+
+PK write valid parameters
+depends_on:MBEDTLS_RSA_C
+valid_parameters_pkwrite:"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"
+
 PK utils: RSA
 depends_on:MBEDTLS_RSA_C:MBEDTLS_GENPRIME
 pk_utils:MBEDTLS_PK_RSA:512:64:"RSA"
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index 4813f71..4e6ab17 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -2,6 +2,8 @@
 #include "mbedtls/pk.h"
 
 /* For error codes */
+#include "mbedtls/asn1.h"
+#include "mbedtls/base64.h"
 #include "mbedtls/ecp.h"
 #include "mbedtls/rsa.h"
 
@@ -70,6 +72,426 @@
  */
 
 /* BEGIN_CASE */
+void valid_parameters( )
+{
+    mbedtls_pk_context pk;
+    unsigned char buf[1];
+    size_t len;
+    void *options = NULL;
+
+    mbedtls_pk_init( &pk );
+
+    TEST_VALID_PARAM( mbedtls_pk_free( NULL ) );
+
+#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
+    TEST_VALID_PARAM( mbedtls_pk_restart_free( NULL ) );
+#endif
+
+    TEST_ASSERT( mbedtls_pk_setup( &pk, NULL ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    /* In informational functions, we accept NULL where a context pointer
+     * is expected because that's what the library has done forever.
+     * We do not document that NULL is accepted, so we may wish to change
+     * the behavior in a future version. */
+    TEST_ASSERT( mbedtls_pk_get_bitlen( NULL ) == 0 );
+    TEST_ASSERT( mbedtls_pk_get_len( NULL ) == 0 );
+    TEST_ASSERT( mbedtls_pk_can_do( NULL, MBEDTLS_PK_NONE ) == 0 );
+
+    TEST_ASSERT( mbedtls_pk_sign_restartable( &pk,
+                                              MBEDTLS_MD_NONE,
+                                              NULL, 0,
+                                              buf, &len,
+                                              rnd_std_rand, NULL,
+                                              NULL ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_pk_sign_restartable( &pk,
+                                              MBEDTLS_MD_NONE,
+                                              NULL, 0,
+                                              buf, &len,
+                                              rnd_std_rand, NULL,
+                                              NULL ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_pk_sign( &pk,
+                                  MBEDTLS_MD_NONE,
+                                  NULL, 0,
+                                  buf, &len,
+                                  rnd_std_rand, NULL ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_pk_verify_restartable( &pk,
+                                                MBEDTLS_MD_NONE,
+                                                NULL, 0,
+                                                buf, sizeof( buf ),
+                                                NULL ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_pk_verify( &pk,
+                                    MBEDTLS_MD_NONE,
+                                    NULL, 0,
+                                    buf, sizeof( buf ) ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_pk_verify_ext( MBEDTLS_PK_NONE, options,
+                                        &pk,
+                                        MBEDTLS_MD_NONE,
+                                        NULL, 0,
+                                        buf, sizeof( buf ) ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_pk_encrypt( &pk,
+                                     NULL, 0,
+                                     NULL, &len, 0,
+                                     rnd_std_rand, NULL ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_pk_decrypt( &pk,
+                                     NULL, 0,
+                                     NULL, &len, 0,
+                                     rnd_std_rand, NULL ) ==
+                 MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+#if defined(MBEDTLS_PK_PARSE_C)
+    TEST_ASSERT( mbedtls_pk_parse_key( &pk, NULL, 0, NULL, 1 ) ==
+                 MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
+
+    TEST_ASSERT( mbedtls_pk_parse_public_key( &pk, NULL, 0 ) ==
+                 MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
+#endif /* MBEDTLS_PK_PARSE_C */
+}
+/* END_CASE */
+
+/* BEGIN_CASE depends_on:MBEDTLS_PK_WRITE_C */
+void valid_parameters_pkwrite( data_t *key_data )
+{
+    mbedtls_pk_context pk;
+
+    /* For the write tests to be effective, we need a valid key pair. */
+    mbedtls_pk_init( &pk );
+    TEST_ASSERT( mbedtls_pk_parse_key( &pk,
+                                       key_data->x, key_data->len,
+                                       NULL, 0 ) == 0 );
+
+    TEST_ASSERT( mbedtls_pk_write_key_der( &pk, NULL, 0 ) ==
+                 MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
+
+    TEST_ASSERT( mbedtls_pk_write_pubkey_der( &pk, NULL, 0 ) ==
+                 MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
+
+#if defined(MBEDTLS_PEM_WRITE_C)
+    TEST_ASSERT( mbedtls_pk_write_key_pem( &pk, NULL, 0 ) ==
+                 MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
+
+    TEST_ASSERT( mbedtls_pk_write_pubkey_pem( &pk, NULL, 0 ) ==
+                 MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
+#endif /* MBEDTLS_PEM_WRITE_C */
+
+exit:
+    mbedtls_pk_free( &pk );
+}
+/* END_CASE */
+
+/* BEGIN_CASE depends_on:MBEDTLS_CHECK_PARAMS:!MBEDTLS_PARAM_FAILED_ALT */
+void invalid_parameters( )
+{
+    size_t len;
+    unsigned char *null_buf = NULL;
+    unsigned char buf[1];
+    unsigned char *p = buf;
+    char str[1] = {0};
+    mbedtls_pk_context pk;
+    mbedtls_md_type_t valid_md = MBEDTLS_MD_SHA256;
+    void *options = buf;
+
+    (void) null_buf;
+    (void) p;
+    (void) str;
+
+    mbedtls_pk_init( &pk );
+
+    TEST_INVALID_PARAM( mbedtls_pk_init( NULL ) );
+
+#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
+    TEST_INVALID_PARAM( mbedtls_pk_restart_init( NULL ) );
+#endif
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_setup( NULL, NULL ) );
+
+#if defined(MBEDTLS_PK_RSA_ALT_SUPPORT)
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_setup_rsa_alt( NULL, buf,
+                                                      NULL, NULL, NULL ) );
+#endif
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify_restartable( NULL,
+                                                           MBEDTLS_MD_NONE,
+                                                           buf, sizeof( buf ),
+                                                           buf, sizeof( buf ),
+                                                           NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify_restartable( &pk,
+                                                           MBEDTLS_MD_NONE,
+                                                           NULL, sizeof( buf ),
+                                                           buf, sizeof( buf ),
+                                                           NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify_restartable( &pk,
+                                                           valid_md,
+                                                           NULL, 0,
+                                                           buf, sizeof( buf ),
+                                                           NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify_restartable( &pk,
+                                                           MBEDTLS_MD_NONE,
+                                                           buf, sizeof( buf ),
+                                                           NULL, sizeof( buf ),
+                                                           NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify( NULL,
+                                               MBEDTLS_MD_NONE,
+                                               buf, sizeof( buf ),
+                                               buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify( &pk,
+                                               MBEDTLS_MD_NONE,
+                                               NULL, sizeof( buf ),
+                                               buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify( &pk,
+                                               valid_md,
+                                               NULL, 0,
+                                               buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify( &pk,
+                                               MBEDTLS_MD_NONE,
+                                               buf, sizeof( buf ),
+                                               NULL, sizeof( buf ) ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify_ext( MBEDTLS_PK_NONE, options,
+                                                   NULL,
+                                                   MBEDTLS_MD_NONE,
+                                                   buf, sizeof( buf ),
+                                                   buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify_ext( MBEDTLS_PK_NONE, options,
+                                                   &pk,
+                                                   MBEDTLS_MD_NONE,
+                                                   NULL, sizeof( buf ),
+                                                   buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify_ext( MBEDTLS_PK_NONE, options,
+                                                   &pk,
+                                                   valid_md,
+                                                   NULL, 0,
+                                                   buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_verify_ext( MBEDTLS_PK_NONE, options,
+                                                   &pk,
+                                                   MBEDTLS_MD_NONE,
+                                                   buf, sizeof( buf ),
+                                                   NULL, sizeof( buf ) ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_sign_restartable( NULL,
+                                                         MBEDTLS_MD_NONE,
+                                                         buf, sizeof( buf ),
+                                                         buf, &len,
+                                                         rnd_std_rand, NULL,
+                                                         NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_sign_restartable( &pk,
+                                                         MBEDTLS_MD_NONE,
+                                                         NULL, sizeof( buf ),
+                                                         buf, &len,
+                                                         rnd_std_rand, NULL,
+                                                         NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_sign_restartable( &pk,
+                                                         valid_md,
+                                                         NULL, 0,
+                                                         buf, &len,
+                                                         rnd_std_rand, NULL,
+                                                         NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_sign_restartable( &pk,
+                                                         MBEDTLS_MD_NONE,
+                                                         buf, sizeof( buf ),
+                                                         NULL, &len,
+                                                         rnd_std_rand, NULL,
+                                                         NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_sign( NULL,
+                                             MBEDTLS_MD_NONE,
+                                             buf, sizeof( buf ),
+                                             buf, &len,
+                                             rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_sign( &pk,
+                                             MBEDTLS_MD_NONE,
+                                             NULL, sizeof( buf ),
+                                             buf, &len,
+                                             rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_sign( &pk,
+                                             valid_md,
+                                             NULL, 0,
+                                             buf, &len,
+                                             rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_sign( &pk,
+                                             MBEDTLS_MD_NONE,
+                                             buf, sizeof( buf ),
+                                             NULL, &len,
+                                             rnd_std_rand, NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_decrypt( NULL,
+                                                buf, sizeof( buf ),
+                                                buf, &len, sizeof( buf ),
+                                                rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_decrypt( &pk,
+                                                NULL, sizeof( buf ),
+                                                buf, &len, sizeof( buf ),
+                                                rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_decrypt( &pk,
+                                                buf, sizeof( buf ),
+                                                NULL, &len, sizeof( buf ),
+                                                rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_decrypt( &pk,
+                                                buf, sizeof( buf ),
+                                                buf, NULL, sizeof( buf ),
+                                                rnd_std_rand, NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_encrypt( NULL,
+                                                buf, sizeof( buf ),
+                                                buf, &len, sizeof( buf ),
+                                                rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_encrypt( &pk,
+                                                NULL, sizeof( buf ),
+                                                buf, &len, sizeof( buf ),
+                                                rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_encrypt( &pk,
+                                                buf, sizeof( buf ),
+                                                NULL, &len, sizeof( buf ),
+                                                rnd_std_rand, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_encrypt( &pk,
+                                                buf, sizeof( buf ),
+                                                buf, NULL, sizeof( buf ),
+                                                rnd_std_rand, NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_check_pair( NULL, &pk ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_check_pair( &pk, NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_debug( NULL, NULL ) );
+
+#if defined(MBEDTLS_PK_PARSE_C)
+#if defined(MBEDTLS_FS_IO)
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_load_file( NULL, &p, &len ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_load_file( str, NULL, &len ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_load_file( str, &p, NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_keyfile( NULL, str, NULL ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_keyfile( &pk, NULL, NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_public_keyfile( NULL, str ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_public_keyfile( &pk, NULL ) );
+#endif
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_subpubkey( NULL, buf, &pk ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_subpubkey( &null_buf, buf, &pk ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_subpubkey( &p, NULL, &pk ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_subpubkey( &p, buf, NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_key( NULL,
+                                                  buf, sizeof( buf ),
+                                                  buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_key( &pk,
+                                                  NULL, sizeof( buf ),
+                                                  buf, sizeof( buf ) ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_public_key( NULL,
+                                                         buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_parse_public_key( &pk,
+                                                         NULL, sizeof( buf ) ) );
+#endif /* MBEDTLS_PK_PARSE_C */
+
+#if defined(MBEDTLS_PK_WRITE_C)
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_pubkey( NULL, p, &pk ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_pubkey( &null_buf, p, &pk ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_pubkey( &p, NULL, &pk ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_pubkey( &p, p, NULL ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_pubkey_der( NULL,
+                                                         buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_pubkey_der( &pk,
+                                                         NULL, sizeof( buf ) ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_key_der( NULL,
+                                                      buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_key_der( &pk,
+                                                      NULL, sizeof( buf ) ) );
+
+#if defined(MBEDTLS_PEM_WRITE_C)
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_pubkey_pem( NULL,
+                                                         buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_pubkey_pem( &pk,
+                                                         NULL, sizeof( buf ) ) );
+
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_key_pem( NULL,
+                                                      buf, sizeof( buf ) ) );
+    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_PK_BAD_INPUT_DATA,
+                            mbedtls_pk_write_key_pem( &pk,
+                                                      NULL, sizeof( buf ) ) );
+#endif /* MBEDTLS_PEM_WRITE_C */
+
+#endif /* MBEDTLS_PK_WRITE_C */
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
 void pk_utils( int type, int size, int len, char * name )
 {
     mbedtls_pk_context pk;