diff --git a/library/rsa_internal.h b/library/rsa_internal.h
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+++ b/library/rsa_internal.h
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+/**
+ * \file rsa_internal.h
+ *
+ * \brief Internal-only RSA public-key cryptosystem API.
+ *
+ * This file declares RSA-related functions that are to be used
+ * only from within the Mbed TLS library itself.
+ *
+ */
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+#ifndef MBEDTLS_RSA_INTERNAL_H
+#define MBEDTLS_RSA_INTERNAL_H
+
+#include "mbedtls/rsa.h"
+#include "mbedtls/asn1.h"
+
+/**
+ * \brief           Parse a PKCS#1 (ASN.1) encoded private RSA key.
+ *
+ * \param rsa       The RSA context where parsed data will be stored.
+ * \param key       The buffer that contains the key.
+ * \param keylen    The length of the key buffer in bytes.
+ *
+ * \return          0 on success.
+ * \return          MBEDTLS_ERR_ASN1_xxx in case of ASN.1 parsing errors.
+ * \return          MBEDTLS_ERR_RSA_xxx in case of RSA internal failures while
+ *                  parsing data.
+ * \return          MBEDTLS_ERR_RSA_KEY_CHECK_FAILED if validity checks on the
+ *                  provided key fail.
+ */
+int mbedtls_rsa_parse_key(mbedtls_rsa_context *rsa, const unsigned char *key, size_t keylen);
+
+/**
+ * \brief           Parse a PKCS#1 (ASN.1) encoded public RSA key.
+ *
+ * \param rsa       The RSA context where parsed data will be stored.
+ * \param key       The buffer that contains the key.
+ * \param keylen    The length of the key buffer in bytes.
+ *
+ * \return          0 on success.
+ * \return          MBEDTLS_ERR_ASN1_xxx in case of ASN.1 parsing errors.
+ * \return          MBEDTLS_ERR_RSA_xxx in case of RSA internal failures while
+ *                  parsing data.
+ * \return          MBEDTLS_ERR_RSA_KEY_CHECK_FAILED if validity checks on the
+ *                  provided key fail.
+ */
+int mbedtls_rsa_parse_pubkey(mbedtls_rsa_context *rsa, const unsigned char *key, size_t keylen);
+
+/**
+ * \brief           Write a PKCS#1 (ASN.1) encoded private RSA key.
+ *
+ * \param rsa       The RSA context which contains the data to be written.
+ * \param start     Beginning of the buffer that will be filled with the
+ *                  private key.
+ * \param p         End of the buffer that will be filled with the private key.
+ *                  On successful return, the referenced pointer will be
+ *                  updated in order to point to the beginning of written data.
+ *
+ * \return          On success, the number of bytes written to the output buffer
+ *                  (i.e. a value > 0).
+ * \return          MBEDTLS_ERR_RSA_BAD_INPUT_DATA if the RSA context does not
+ *                  contain a valid key pair.
+ * \return          MBEDTLS_ERR_ASN1_xxx in case of failure while writing to the
+ *                  output buffer.
+ *
+ * \note            The output buffer is filled backward, i.e. starting from its
+ *                  end and moving toward its start.
+ */
+int mbedtls_rsa_write_key(const mbedtls_rsa_context *rsa, unsigned char *start,
+                          unsigned char **p);
+
+/**
+ * \brief           Parse a PKCS#1 (ASN.1) encoded public RSA key.
+ *
+ * \param rsa       The RSA context which contains the data to be written.
+ * \param start     Beginning of the buffer that will be filled with the
+ *                  private key.
+ * \param p         End of the buffer that will be filled with the private key.
+ *                  On successful return, the referenced pointer will be
+ *                  updated in order to point to the beginning of written data.
+ *
+ * \return          On success, the number of bytes written to the output buffer
+ *                  (i.e. a value > 0).
+ * \return          MBEDTLS_ERR_RSA_BAD_INPUT_DATA if the RSA context does not
+ *                  contain a valid public key.
+ * \return          MBEDTLS_ERR_ASN1_xxx in case of failure while writing to the
+ *                  output buffer.
+ *
+ * \note            The output buffer is filled backward, i.e. starting from its
+ *                  end and moving toward its start.
+ */
+int mbedtls_rsa_write_pubkey(const mbedtls_rsa_context *rsa, unsigned char *start,
+                             unsigned char **p);
+
+#if defined(MBEDTLS_PKCS1_V21)
+/**
+ * \brief This function is analogue to \c mbedtls_rsa_rsassa_pss_sign().
+ *        The only difference between them is that this function is more flexible
+ *        on the parameters of \p ctx that are set with \c mbedtls_rsa_set_padding().
+ *
+ * \note  Compared to its counterpart, this function:
+ *        - does not check the padding setting of \p ctx.
+ *        - allows the hash_id of \p ctx to be MBEDTLS_MD_NONE,
+ *          in which case it uses \p md_alg as the hash_id.
+ *
+ * \note  Refer to \c mbedtls_rsa_rsassa_pss_sign() for a description
+ *        of the functioning and parameters of this function.
+ */
+int mbedtls_rsa_rsassa_pss_sign_no_mode_check(mbedtls_rsa_context *ctx,
+                                              int (*f_rng)(void *, unsigned char *, size_t),
+                                              void *p_rng,
+                                              mbedtls_md_type_t md_alg,
+                                              unsigned int hashlen,
+                                              const unsigned char *hash,
+                                              unsigned char *sig);
+#endif /* MBEDTLS_PKCS1_V21 */
+
+#endif /* rsa_internal.h */