diff --git a/library/rsa_alt_helpers.h b/library/rsa_alt_helpers.h
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+/**
+ * \file rsa_alt_helpers.h
+ *
+ * \brief Context-independent RSA helper functions
+ *
+ *  This module declares some RSA-related helper functions useful when
+ *  implementing the RSA interface. These functions are provided in a separate
+ *  compilation unit in order to make it easy for designers of alternative RSA
+ *  implementations to use them in their own code, as it is conceived that the
+ *  functionality they provide will be necessary for most complete
+ *  implementations.
+ *
+ *  End-users of Mbed TLS who are not providing their own alternative RSA
+ *  implementations should not use these functions directly, and should instead
+ *  use only the functions declared in rsa.h.
+ *
+ *  The interface provided by this module will be maintained through LTS (Long
+ *  Term Support) branches of Mbed TLS, but may otherwise be subject to change,
+ *  and must be considered an internal interface of the library.
+ *
+ *  There are two classes of helper functions:
+ *
+ *  (1) Parameter-generating helpers. These are:
+ *      - mbedtls_rsa_deduce_primes
+ *      - mbedtls_rsa_deduce_private_exponent
+ *      - mbedtls_rsa_deduce_crt
+ *       Each of these functions takes a set of core RSA parameters and
+ *       generates some other, or CRT related parameters.
+ *
+ *  (2) Parameter-checking helpers. These are:
+ *      - mbedtls_rsa_validate_params
+ *      - mbedtls_rsa_validate_crt
+ *      They take a set of core or CRT related RSA parameters and check their
+ *      validity.
+ *
+ */
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  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.
+ *
+ */
+
+#ifndef MBEDTLS_RSA_INTERNAL_H
+#define MBEDTLS_RSA_INTERNAL_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#include "mbedtls/bignum.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/**
+ * \brief          Compute RSA prime moduli P, Q from public modulus N=PQ
+ *                 and a pair of private and public key.
+ *
+ * \note           This is a 'static' helper function not operating on
+ *                 an RSA context. Alternative implementations need not
+ *                 overwrite it.
+ *
+ * \param N        RSA modulus N = PQ, with P, Q to be found
+ * \param E        RSA public exponent
+ * \param D        RSA private exponent
+ * \param P        Pointer to MPI holding first prime factor of N on success
+ * \param Q        Pointer to MPI holding second prime factor of N on success
+ *
+ * \return
+ *                 - 0 if successful. In this case, P and Q constitute a
+ *                   factorization of N.
+ *                 - A non-zero error code otherwise.
+ *
+ * \note           It is neither checked that P, Q are prime nor that
+ *                 D, E are modular inverses wrt. P-1 and Q-1. For that,
+ *                 use the helper function \c mbedtls_rsa_validate_params.
+ *
+ */
+int mbedtls_rsa_deduce_primes( mbedtls_mpi const *N, mbedtls_mpi const *E,
+                               mbedtls_mpi const *D,
+                               mbedtls_mpi *P, mbedtls_mpi *Q );
+
+/**
+ * \brief          Compute RSA private exponent from
+ *                 prime moduli and public key.
+ *
+ * \note           This is a 'static' helper function not operating on
+ *                 an RSA context. Alternative implementations need not
+ *                 overwrite it.
+ *
+ * \param P        First prime factor of RSA modulus
+ * \param Q        Second prime factor of RSA modulus
+ * \param E        RSA public exponent
+ * \param D        Pointer to MPI holding the private exponent on success.
+ *
+ * \return
+ *                 - 0 if successful. In this case, D is set to a simultaneous
+ *                   modular inverse of E modulo both P-1 and Q-1.
+ *                 - A non-zero error code otherwise.
+ *
+ * \note           This function does not check whether P and Q are primes.
+ *
+ */
+int mbedtls_rsa_deduce_private_exponent( mbedtls_mpi const *P,
+                                         mbedtls_mpi const *Q,
+                                         mbedtls_mpi const *E,
+                                         mbedtls_mpi *D );
+
+
+/**
+ * \brief          Generate RSA-CRT parameters
+ *
+ * \note           This is a 'static' helper function not operating on
+ *                 an RSA context. Alternative implementations need not
+ *                 overwrite it.
+ *
+ * \param P        First prime factor of N
+ * \param Q        Second prime factor of N
+ * \param D        RSA private exponent
+ * \param DP       Output variable for D modulo P-1
+ * \param DQ       Output variable for D modulo Q-1
+ * \param QP       Output variable for the modular inverse of Q modulo P.
+ *
+ * \return         0 on success, non-zero error code otherwise.
+ *
+ * \note           This function does not check whether P, Q are
+ *                 prime and whether D is a valid private exponent.
+ *
+ */
+int mbedtls_rsa_deduce_crt( const mbedtls_mpi *P, const mbedtls_mpi *Q,
+                            const mbedtls_mpi *D, mbedtls_mpi *DP,
+                            mbedtls_mpi *DQ, mbedtls_mpi *QP );
+
+
+/**
+ * \brief          Check validity of core RSA parameters
+ *
+ * \note           This is a 'static' helper function not operating on
+ *                 an RSA context. Alternative implementations need not
+ *                 overwrite it.
+ *
+ * \param N        RSA modulus N = PQ
+ * \param P        First prime factor of N
+ * \param Q        Second prime factor of N
+ * \param D        RSA private exponent
+ * \param E        RSA public exponent
+ * \param f_rng    PRNG to be used for primality check, or NULL
+ * \param p_rng    PRNG context for f_rng, or NULL
+ *
+ * \return
+ *                 - 0 if the following conditions are satisfied
+ *                   if all relevant parameters are provided:
+ *                    - P prime if f_rng != NULL (%)
+ *                    - Q prime if f_rng != NULL (%)
+ *                    - 1 < N = P * Q
+ *                    - 1 < D, E < N
+ *                    - D and E are modular inverses modulo P-1 and Q-1
+ *                   (%) This is only done if MBEDTLS_GENPRIME is defined.
+ *                 - A non-zero error code otherwise.
+ *
+ * \note           The function can be used with a restricted set of arguments
+ *                 to perform specific checks only. E.g., calling it with
+ *                 (-,P,-,-,-) and a PRNG amounts to a primality check for P.
+ */
+int mbedtls_rsa_validate_params( const mbedtls_mpi *N, const mbedtls_mpi *P,
+                                 const mbedtls_mpi *Q, const mbedtls_mpi *D,
+                                 const mbedtls_mpi *E,
+                                 int (*f_rng)(void *, unsigned char *, size_t),
+                                 void *p_rng );
+
+/**
+ * \brief          Check validity of RSA CRT parameters
+ *
+ * \note           This is a 'static' helper function not operating on
+ *                 an RSA context. Alternative implementations need not
+ *                 overwrite it.
+ *
+ * \param P        First prime factor of RSA modulus
+ * \param Q        Second prime factor of RSA modulus
+ * \param D        RSA private exponent
+ * \param DP       MPI to check for D modulo P-1
+ * \param DQ       MPI to check for D modulo P-1
+ * \param QP       MPI to check for the modular inverse of Q modulo P.
+ *
+ * \return
+ *                 - 0 if the following conditions are satisfied:
+ *                    - D = DP mod P-1 if P, D, DP != NULL
+ *                    - Q = DQ mod P-1 if P, D, DQ != NULL
+ *                    - QP = Q^-1 mod P if P, Q, QP != NULL
+ *                 - \c MBEDTLS_ERR_RSA_KEY_CHECK_FAILED if check failed,
+ *                   potentially including \c MBEDTLS_ERR_MPI_XXX if some
+ *                   MPI calculations failed.
+ *                 - \c MBEDTLS_ERR_RSA_BAD_INPUT_DATA if insufficient
+ *                   data was provided to check DP, DQ or QP.
+ *
+ * \note           The function can be used with a restricted set of arguments
+ *                 to perform specific checks only. E.g., calling it with the
+ *                 parameters (P, -, D, DP, -, -) will check DP = D mod P-1.
+ */
+int mbedtls_rsa_validate_crt( const mbedtls_mpi *P,  const mbedtls_mpi *Q,
+                              const mbedtls_mpi *D,  const mbedtls_mpi *DP,
+                              const mbedtls_mpi *DQ, const mbedtls_mpi *QP );
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* rsa_alt_helpers.h */