diff --git a/library/x509_internal.h b/library/x509_internal.h
new file mode 100644
index 0000000..e1be393
--- /dev/null
+++ b/library/x509_internal.h
@@ -0,0 +1,213 @@
+/**
+ * \file x509.h
+ *
+ * \brief Internal part of the public "x509.h".
+ */
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+#ifndef MBEDTLS_X509_INTERNAL_H
+#define MBEDTLS_X509_INTERNAL_H
+#include "mbedtls/private_access.h"
+
+#include "mbedtls/build_info.h"
+
+#include "mbedtls/x509.h"
+#include "mbedtls/asn1.h"
+#include "mbedtls/pk.h"
+
+#if defined(MBEDTLS_RSA_C)
+#include "mbedtls/rsa.h"
+#endif
+
+/**
+ * \brief          Return the next relative DN in an X509 name.
+ *
+ * \note           Intended use is to compare function result to dn->next
+ *                 in order to detect boundaries of multi-valued RDNs.
+ *
+ * \param dn       Current node in the X509 name
+ *
+ * \return         Pointer to the first attribute-value pair of the
+ *                 next RDN in sequence, or NULL if end is reached.
+ */
+static inline mbedtls_x509_name *mbedtls_x509_dn_get_next(
+    mbedtls_x509_name *dn)
+{
+    while (dn->MBEDTLS_PRIVATE(next_merged) && dn->next != NULL) {
+        dn = dn->next;
+    }
+    return dn->next;
+}
+
+/**
+ * \brief          Store the certificate serial in printable form into buf;
+ *                 no more than size characters will be written.
+ *
+ * \param buf      Buffer to write to
+ * \param size     Maximum size of buffer
+ * \param serial   The X509 serial to represent
+ *
+ * \return         The length of the string written (not including the
+ *                 terminated nul byte), or a negative error code.
+ */
+int mbedtls_x509_serial_gets(char *buf, size_t size, const mbedtls_x509_buf *serial);
+
+/**
+ * \brief          Compare pair of mbedtls_x509_time.
+ *
+ * \param t1       mbedtls_x509_time to compare
+ * \param t2       mbedtls_x509_time to compare
+ *
+ * \return         < 0 if t1 is before t2
+ *                   0 if t1 equals t2
+ *                 > 0 if t1 is after t2
+ */
+int mbedtls_x509_time_cmp(const mbedtls_x509_time *t1, const mbedtls_x509_time *t2);
+
+#if defined(MBEDTLS_HAVE_TIME_DATE)
+/**
+ * \brief          Fill mbedtls_x509_time with provided mbedtls_time_t.
+ *
+ * \param tt       mbedtls_time_t to convert
+ * \param now      mbedtls_x509_time to fill with converted mbedtls_time_t
+ *
+ * \return         \c 0 on success
+ * \return         A non-zero return value on failure.
+ */
+int mbedtls_x509_time_gmtime(mbedtls_time_t tt, mbedtls_x509_time *now);
+#endif /* MBEDTLS_HAVE_TIME_DATE */
+
+/**
+ * \brief          Check a given mbedtls_x509_time against the system time
+ *                 and tell if it's in the past.
+ *
+ * \note           Intended usage is "if( is_past( valid_to ) ) ERROR".
+ *                 Hence the return value of 1 if on internal errors.
+ *
+ * \param to       mbedtls_x509_time to check
+ *
+ * \return         1 if the given time is in the past or an error occurred,
+ *                 0 otherwise.
+ */
+int mbedtls_x509_time_is_past(const mbedtls_x509_time *to);
+
+/**
+ * \brief          Check a given mbedtls_x509_time against the system time
+ *                 and tell if it's in the future.
+ *
+ * \note           Intended usage is "if( is_future( valid_from ) ) ERROR".
+ *                 Hence the return value of 1 if on internal errors.
+ *
+ * \param from     mbedtls_x509_time to check
+ *
+ * \return         1 if the given time is in the future or an error occurred,
+ *                 0 otherwise.
+ */
+int mbedtls_x509_time_is_future(const mbedtls_x509_time *from);
+
+/**
+ * \brief          This function parses an item in the SubjectAlternativeNames
+ *                 extension. Please note that this function might allocate
+ *                 additional memory for a subject alternative name, thus
+ *                 mbedtls_x509_free_subject_alt_name has to be called
+ *                 to dispose of this additional memory afterwards.
+ *
+ * \param san_buf  The buffer holding the raw data item of the subject
+ *                 alternative name.
+ * \param san      The target structure to populate with the parsed presentation
+ *                 of the subject alternative name encoded in \p san_buf.
+ *
+ * \note           Supported GeneralName types, as defined in RFC 5280:
+ *                 "rfc822Name", "dnsName", "directoryName",
+ *                 "uniformResourceIdentifier" and "hardware_module_name"
+ *                 of type "otherName", as defined in RFC 4108.
+ *
+ * \note           This function should be called on a single raw data of
+ *                 subject alternative name. For example, after successful
+ *                 certificate parsing, one must iterate on every item in the
+ *                 \c crt->subject_alt_names sequence, and pass it to
+ *                 this function.
+ *
+ * \warning        The target structure contains pointers to the raw data of the
+ *                 parsed certificate, and its lifetime is restricted by the
+ *                 lifetime of the certificate.
+ *
+ * \return         \c 0 on success
+ * \return         #MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE for an unsupported
+ *                 SAN type.
+ * \return         Another negative value for any other failure.
+ */
+int mbedtls_x509_parse_subject_alt_name(const mbedtls_x509_buf *san_buf,
+                                        mbedtls_x509_subject_alternative_name *san);
+/**
+ * \brief          Unallocate all data related to subject alternative name
+ *
+ * \param san      SAN structure - extra memory owned by this structure will be freed
+ */
+void mbedtls_x509_free_subject_alt_name(mbedtls_x509_subject_alternative_name *san);
+
+int mbedtls_x509_get_name(unsigned char **p, const unsigned char *end,
+                          mbedtls_x509_name *cur);
+int mbedtls_x509_get_alg_null(unsigned char **p, const unsigned char *end,
+                              mbedtls_x509_buf *alg);
+int mbedtls_x509_get_alg(unsigned char **p, const unsigned char *end,
+                         mbedtls_x509_buf *alg, mbedtls_x509_buf *params);
+#if defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT)
+int mbedtls_x509_get_rsassa_pss_params(const mbedtls_x509_buf *params,
+                                       mbedtls_md_type_t *md_alg, mbedtls_md_type_t *mgf_md,
+                                       int *salt_len);
+#endif
+int mbedtls_x509_get_sig(unsigned char **p, const unsigned char *end, mbedtls_x509_buf *sig);
+int mbedtls_x509_get_sig_alg(const mbedtls_x509_buf *sig_oid, const mbedtls_x509_buf *sig_params,
+                             mbedtls_md_type_t *md_alg, mbedtls_pk_type_t *pk_alg,
+                             void **sig_opts);
+int mbedtls_x509_get_time(unsigned char **p, const unsigned char *end,
+                          mbedtls_x509_time *t);
+int mbedtls_x509_get_serial(unsigned char **p, const unsigned char *end,
+                            mbedtls_x509_buf *serial);
+int mbedtls_x509_get_ext(unsigned char **p, const unsigned char *end,
+                         mbedtls_x509_buf *ext, int tag);
+#if !defined(MBEDTLS_X509_REMOVE_INFO)
+int mbedtls_x509_sig_alg_gets(char *buf, size_t size, const mbedtls_x509_buf *sig_oid,
+                              mbedtls_pk_type_t pk_alg, mbedtls_md_type_t md_alg,
+                              const void *sig_opts);
+#endif
+int mbedtls_x509_key_size_helper(char *buf, size_t buf_size, const char *name);
+int mbedtls_x509_set_extension(mbedtls_asn1_named_data **head, const char *oid, size_t oid_len,
+                               int critical, const unsigned char *val,
+                               size_t val_len);
+int mbedtls_x509_write_extensions(unsigned char **p, unsigned char *start,
+                                  mbedtls_asn1_named_data *first);
+int mbedtls_x509_write_names(unsigned char **p, unsigned char *start,
+                             mbedtls_asn1_named_data *first);
+int mbedtls_x509_write_sig(unsigned char **p, unsigned char *start,
+                           const char *oid, size_t oid_len,
+                           unsigned char *sig, size_t size,
+                           mbedtls_pk_type_t pk_alg);
+int mbedtls_x509_get_ns_cert_type(unsigned char **p,
+                                  const unsigned char *end,
+                                  unsigned char *ns_cert_type);
+int mbedtls_x509_get_key_usage(unsigned char **p,
+                               const unsigned char *end,
+                               unsigned int *key_usage);
+int mbedtls_x509_get_subject_alt_name(unsigned char **p,
+                                      const unsigned char *end,
+                                      mbedtls_x509_sequence *subject_alt_name);
+int mbedtls_x509_get_subject_alt_name_ext(unsigned char **p,
+                                          const unsigned char *end,
+                                          mbedtls_x509_sequence *subject_alt_name);
+int mbedtls_x509_info_subject_alt_name(char **buf, size_t *size,
+                                       const mbedtls_x509_sequence
+                                       *subject_alt_name,
+                                       const char *prefix);
+int mbedtls_x509_info_cert_type(char **buf, size_t *size,
+                                unsigned char ns_cert_type);
+int mbedtls_x509_info_key_usage(char **buf, size_t *size,
+                                unsigned int key_usage);
+
+int mbedtls_x509_write_set_san_common(mbedtls_asn1_named_data **extensions,
+                                      const mbedtls_x509_san_list *san_list);
+
+#endif /* MBEDTLS_X509_INTERNAL_H */