diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index ec004f5..a93b0aa 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1650,6 +1650,7 @@
  *          library/ecp.c
  *          library/ecdsa.c
  *          library/rsa.c
+ *          library/rsa_internal.c
  *          library/ssl_tls.c
  *
  * This module is required for RSA, DHM and ECC (ECDH, ECDSA) support.
@@ -2263,6 +2264,7 @@
  * Enable the RSA public-key cryptosystem.
  *
  * Module:  library/rsa.c
+ *          library/rsa_internal.c
  * Caller:  library/ssl_cli.c
  *          library/ssl_srv.c
  *          library/ssl_tls.c
diff --git a/include/mbedtls/rsa.h b/include/mbedtls/rsa.h
index c85e6c8..eab8e0d 100644
--- a/include/mbedtls/rsa.h
+++ b/include/mbedtls/rsa.h
@@ -74,162 +74,6 @@
 extern "C" {
 #endif
 
-/**
- * Helper functions for RSA-related operations on MPI's.
- */
-
-/**
- * \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 D        RSA private exponent
- * \param E        RSA public 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 *D,
-                               mbedtls_mpi const *E,
-                               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 = PQ
- *                    - 1 < D, E < N
- *                    - D and E are modular inverses modulo P-1 and Q-1
- *                 - 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 );
-
-/**
- * Implementation of RSA interface
- */
-
 #if !defined(MBEDTLS_RSA_ALT)
 
 /**
diff --git a/include/mbedtls/rsa_internal.h b/include/mbedtls/rsa_internal.h
new file mode 100644
index 0000000..2353470
--- /dev/null
+++ b/include/mbedtls/rsa_internal.h
@@ -0,0 +1,219 @@
+/**
+ * \file rsa_internal.h
+ *
+ * \brief Context-independent RSA helper functions
+ *
+ *  Copyright (C) 2006-2017, ARM Limited, All Rights Reserved
+ *  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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ *
+ *
+ *  This file declares some RSA-related helper functions useful when
+ *  implementing the RSA interface. They are public and provided in a
+ *  separate compilation unit in order to make it easy for designers of
+ *  alternative RSA implementations to use them in their code, as it is
+ *  conceived that the functionality they provide will be necessary
+ *  for most complete implementations.
+ *
+ *  End-users of Mbed TLS not intending to re-implement the RSA functionality
+ *  are not expected to get into the need of making use of these functions directly,
+ *  but instead should be able to make do with the implementation of the RSA module.
+ *
+ *  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.
+ *
+ */
+
+#ifndef MBEDTLS_RSA_INTERNAL_H
+#define MBEDTLS_RSA_INTERNAL_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#include "bignum.h"
+
+#if defined(MBEDTLS_RSA_C)
+
+#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 D        RSA private exponent
+ * \param E        RSA public 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 *D,
+                               mbedtls_mpi const *E,
+                               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 = PQ
+ *                    - 1 < D, E < N
+ *                    - D and E are modular inverses modulo P-1 and Q-1
+ *                 - 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 );
+
+
+#endif /* MBEDTLS_RSA_C */
+
+#endif /* rsa_internal.h */
diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index 7a9f185..49f037c 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -48,6 +48,7 @@
     platform.c
     ripemd160.c
     rsa.c
+    rsa_internal.c
     sha1.c
     sha256.c
     sha512.c
diff --git a/library/Makefile b/library/Makefile
index 28f9231..541d47f 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -59,9 +59,9 @@
 		padlock.o	pem.o		pk.o		\
 		pk_wrap.o	pkcs12.o	pkcs5.o		\
 		pkparse.o	pkwrite.o	platform.o	\
-		ripemd160.o	rsa.o		sha1.o		\
-		sha256.o	sha512.o	threading.o	\
-		timing.o	version.o			\
+		ripemd160.o	rsa_internal.o	rsa.o  		\
+		sha1.o		sha256.o	sha512.o	\
+		threading.o	timing.o	version.o	\
 		version_features.o		xtea.o
 
 OBJS_X509=	certs.o		pkcs11.o	x509.o		\
diff --git a/library/rsa.c b/library/rsa.c
index 493cd1c..83e2b2b 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -46,6 +46,7 @@
 #if defined(MBEDTLS_RSA_C)
 
 #include "mbedtls/rsa.h"
+#include "mbedtls/rsa_internal.h"
 #include "mbedtls/oid.h"
 
 #include <string.h>
@@ -67,483 +68,13 @@
 #define mbedtls_free   free
 #endif
 
+#if !defined(MBEDTLS_RSA_ALT)
+
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
-/*
- * Context-independent RSA helper functions.
- *
- * 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.
- *
- * The helper functions do not use the RSA context structure
- * and therefore do not need to be replaced when providing
- * an alternative RSA implementation.
- *
- * Their main purpose is to provide common MPI operations in the context
- * of RSA that can be easily shared across multiple implementations.
- */
-
-/*
- *
- * Given the modulus N=PQ and a pair of public and private
- * exponents E and D, respectively, factor N.
- *
- * Setting F := lcm(P-1,Q-1), the idea is as follows:
- *
- * (a) For any 1 <= X < N with gcd(X,N)=1, we have X^F = 1 modulo N, so X^(F/2)
- *     is a square root of 1 in Z/NZ. Since Z/NZ ~= Z/PZ x Z/QZ by CRT and the
- *     square roots of 1 in Z/PZ and Z/QZ are +1 and -1, this leaves the four
- *     possibilities X^(F/2) = (+-1, +-1). If it happens that X^(F/2) = (-1,+1)
- *     or (+1,-1), then gcd(X^(F/2) + 1, N) will be equal to one of the prime
- *     factors of N.
- *
- * (b) If we don't know F/2 but (F/2) * K for some odd (!) K, then the same
- *     construction still applies since (-)^K is the identity on the set of
- *     roots of 1 in Z/NZ.
- *
- * The public and private key primitives (-)^E and (-)^D are mutually inverse
- * bijections on Z/NZ if and only if (-)^(DE) is the identity on Z/NZ, i.e.
- * if and only if DE - 1 is a multiple of F, say DE - 1 = F * L.
- * Splitting L = 2^t * K with K odd, we have
- *
- *   DE - 1 = FL = (F/2) * (2^(t+1)) * K,
- *
- * so (F / 2) * K is among the numbers
- *
- *   (DE - 1) >> 1, (DE - 1) >> 2, ..., (DE - 1) >> ord
- *
- * where ord is the order of 2 in (DE - 1).
- * We can therefore iterate through these numbers apply the construction
- * of (a) and (b) above to attempt to factor N.
- *
- */
-int mbedtls_rsa_deduce_primes( mbedtls_mpi const *N,
-                     mbedtls_mpi const *D, mbedtls_mpi const *E,
-                     mbedtls_mpi *P, mbedtls_mpi *Q )
-{
-    int ret = 0;
-
-    uint16_t attempt;  /* Number of current attempt  */
-    uint16_t iter;     /* Number of squares computed in the current attempt */
-
-    uint16_t order;    /* Order of 2 in DE - 1 */
-
-    mbedtls_mpi T;  /* Holds largest odd divisor of DE - 1 */
-    mbedtls_mpi K;  /* During factorization attempts, stores a random integer
-                     * in the range of [0,..,N] */
-
-    const unsigned int primes[] = { 2,
-           3,    5,    7,   11,   13,   17,   19,   23,
-          29,   31,   37,   41,   43,   47,   53,   59,
-          61,   67,   71,   73,   79,   83,   89,   97,
-         101,  103,  107,  109,  113,  127,  131,  137,
-         139,  149,  151,  157,  163,  167,  173,  179,
-         181,  191,  193,  197,  199,  211,  223,  227,
-         229,  233,  239,  241,  251,  257,  263,  269,
-         271,  277,  281,  283,  293,  307,  311,  313
-    };
-
-    const size_t num_primes = sizeof( primes ) / sizeof( *primes );
-
-    if( P == NULL || Q == NULL || P->p != NULL || Q->p != NULL )
-        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
-
-    if( mbedtls_mpi_cmp_int( N, 0 ) <= 0 ||
-        mbedtls_mpi_cmp_int( D, 1 ) <= 0 ||
-        mbedtls_mpi_cmp_mpi( D, N ) >= 0 ||
-        mbedtls_mpi_cmp_int( E, 1 ) <= 0 ||
-        mbedtls_mpi_cmp_mpi( E, N ) >= 0 )
-    {
-        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
-    }
-
-    /*
-     * Initializations and temporary changes
-     */
-
-    mbedtls_mpi_init( &K );
-    mbedtls_mpi_init( &T );
-
-    /* T := DE - 1 */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T, D,  E ) );
-    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &T, &T, 1 ) );
-
-    if( ( order = mbedtls_mpi_lsb( &T ) ) == 0 )
-    {
-        ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
-        goto cleanup;
-    }
-
-    /* After this operation, T holds the largest odd divisor of DE - 1. */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &T, order ) );
-
-    /*
-     * Actual work
-     */
-
-    /* Skip trying 2 if N == 1 mod 8 */
-    attempt = 0;
-    if( N->p[0] % 8 == 1 )
-        attempt = 1;
-
-    for( ; attempt < num_primes; ++attempt )
-    {
-        mbedtls_mpi_lset( &K, primes[attempt] );
-
-        /* Check if gcd(K,N) = 1 */
-        MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( P, &K, N ) );
-        if( mbedtls_mpi_cmp_int( P, 1 ) != 0 )
-            continue;
-
-        /* Go through K^T + 1, K^(2T) + 1, K^(4T) + 1, ...
-         * and check whether they have nontrivial GCD with N. */
-        MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &K, &K, &T, N,
-                             Q /* temporarily use Q for storing Montgomery
-                                * multiplication helper values */ ) );
-
-        for( iter = 1; iter < order; ++iter )
-        {
-            MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( &K, &K, 1 ) );
-            MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( P, &K, N ) );
-
-            if( mbedtls_mpi_cmp_int( P, 1 ) ==  1 &&
-                mbedtls_mpi_cmp_mpi( P, N ) == -1 )
-            {
-                /*
-                 * Have found a nontrivial divisor P of N.
-                 * Set Q := N / P.
-                 */
-
-                MBEDTLS_MPI_CHK( mbedtls_mpi_div_mpi( Q, NULL, N, P ) );
-                goto cleanup;
-            }
-
-            MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, &K, 1 ) );
-            MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, &K, &K ) );
-            MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &K, &K, N ) );
-        }
-    }
-
-    ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
-
-cleanup:
-
-    mbedtls_mpi_free( &K );
-    mbedtls_mpi_free( &T );
-    return( ret );
-}
-
-/*
- * Given P, Q and the public exponent E, deduce D.
- * This is essentially a modular inversion.
- */
-
-int mbedtls_rsa_deduce_private_exponent( mbedtls_mpi const *P,
-                                         mbedtls_mpi const *Q,
-                                         mbedtls_mpi const *E,
-                                         mbedtls_mpi *D )
-{
-    int ret = 0;
-    mbedtls_mpi K, L;
-
-    if( D == NULL || mbedtls_mpi_cmp_int( D, 0 ) != 0 )
-        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
-
-    if( mbedtls_mpi_cmp_int( P, 1 ) <= 0 ||
-        mbedtls_mpi_cmp_int( Q, 1 ) <= 0 ||
-        mbedtls_mpi_cmp_int( E, 0 ) == 0 )
-    {
-        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
-    }
-
-    mbedtls_mpi_init( &K );
-    mbedtls_mpi_init( &L );
-
-    /* Temporarily put K := P-1 and L := Q-1 */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, P, 1 ) );
-    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &L, Q, 1 ) );
-
-    /* Temporarily put D := gcd(P-1, Q-1) */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( D, &K, &L ) );
-
-    /* K := LCM(P-1, Q-1) */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, &K, &L ) );
-    MBEDTLS_MPI_CHK( mbedtls_mpi_div_mpi( &K, NULL, &K, D ) );
-
-    /* Compute modular inverse of E in LCM(P-1, Q-1) */
-    MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( D, E, &K ) );
-
-cleanup:
-
-    mbedtls_mpi_free( &K );
-    mbedtls_mpi_free( &L );
-
-    return( ret );
-}
-
-/*
- * Check that RSA CRT parameters are in accordance with core parameters.
- */
-
-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 )
-{
-    int ret = 0;
-
-    mbedtls_mpi K, L;
-    mbedtls_mpi_init( &K );
-    mbedtls_mpi_init( &L );
-
-    /* Check that DP - D == 0 mod P - 1 */
-    if( DP != NULL )
-    {
-        if( P == NULL )
-        {
-            ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
-            goto cleanup;
-        }
-
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, P, 1 ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &L, DP, D ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &L, &L, &K ) );
-
-        if( mbedtls_mpi_cmp_int( &L, 0 ) != 0 )
-        {
-            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-            goto cleanup;
-        }
-    }
-
-    /* Check that DQ - D == 0 mod Q - 1 */
-    if( DQ != NULL )
-    {
-        if( Q == NULL )
-        {
-            ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
-            goto cleanup;
-        }
-
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, Q, 1 ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &L, DQ, D ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &L, &L, &K ) );
-
-        if( mbedtls_mpi_cmp_int( &L, 0 ) != 0 )
-        {
-            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-            goto cleanup;
-        }
-    }
-
-    /* Check that QP * Q - 1 == 0 mod P */
-    if( QP != NULL )
-    {
-        if( P == NULL || Q == NULL )
-        {
-            ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
-            goto cleanup;
-        }
-
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, QP, Q ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, &K, 1 ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &K, &K, P ) );
-        if( mbedtls_mpi_cmp_int( &K, 0 ) != 0 )
-        {
-            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-            goto cleanup;
-        }
-    }
-
-cleanup:
-
-    /* Wrap MPI error codes by RSA check failure error code */
-    if( ret != 0 &&
-        ret != MBEDTLS_ERR_RSA_KEY_CHECK_FAILED &&
-        ret != MBEDTLS_ERR_RSA_BAD_INPUT_DATA )
-    {
-        ret += MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-    }
-
-    mbedtls_mpi_free( &K );
-    mbedtls_mpi_free( &L );
-
-    return( ret );
-}
-
-/*
- * Check that core RSA parameters are sane.
- */
-
-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 )
-{
-    int ret = 0;
-    mbedtls_mpi K, L;
-
-    mbedtls_mpi_init( &K );
-    mbedtls_mpi_init( &L );
-
-    /*
-     * Step 1: If PRNG provided, check that P and Q are prime
-     */
-
-#if defined(MBEDTLS_GENPRIME)
-    if( f_rng != NULL && P != NULL &&
-        ( ret = mbedtls_mpi_is_prime( P, f_rng, p_rng ) ) != 0 )
-    {
-        ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-        goto cleanup;
-    }
-
-    if( f_rng != NULL && Q != NULL &&
-        ( ret = mbedtls_mpi_is_prime( Q, f_rng, p_rng ) ) != 0 )
-    {
-        ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-        goto cleanup;
-    }
-#else
-    ((void) f_rng);
-    ((void) p_rng);
-#endif /* MBEDTLS_GENPRIME */
-
-    /*
-     * Step 2: Check that 1 < N = PQ
-     */
-
-    if( P != NULL && Q != NULL && N != NULL )
-    {
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, P, Q ) );
-        if( mbedtls_mpi_cmp_int( N, 1 )  <= 0 ||
-            mbedtls_mpi_cmp_mpi( &K, N ) != 0 )
-        {
-            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-            goto cleanup;
-        }
-    }
-
-    /*
-     * Step 3: Check and 1 < D, E < N if present.
-     */
-
-    if( N != NULL && D != NULL && E != NULL )
-    {
-        if ( mbedtls_mpi_cmp_int( D, 1 ) <= 0 ||
-             mbedtls_mpi_cmp_int( E, 1 ) <= 0 ||
-             mbedtls_mpi_cmp_mpi( D, N ) >= 0 ||
-             mbedtls_mpi_cmp_mpi( E, N ) >= 0 )
-        {
-            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-            goto cleanup;
-        }
-    }
-
-    /*
-     * Step 4: Check that D, E are inverse modulo P-1 and Q-1
-     */
-
-    if( P != NULL && Q != NULL && D != NULL && E != NULL )
-    {
-        if( mbedtls_mpi_cmp_int( P, 1 ) <= 0 ||
-            mbedtls_mpi_cmp_int( Q, 1 ) <= 0 )
-        {
-            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-            goto cleanup;
-        }
-
-        /* Compute DE-1 mod P-1 */
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, D, E ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, &K, 1 ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &L, P, 1 ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &K, &K, &L ) );
-        if( mbedtls_mpi_cmp_int( &K, 0 ) != 0 )
-        {
-            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-            goto cleanup;
-        }
-
-        /* Compute DE-1 mod Q-1 */
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, D, E ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, &K, 1 ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &L, Q, 1 ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &K, &K, &L ) );
-        if( mbedtls_mpi_cmp_int( &K, 0 ) != 0 )
-        {
-            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-            goto cleanup;
-        }
-    }
-
-cleanup:
-
-    mbedtls_mpi_free( &K );
-    mbedtls_mpi_free( &L );
-
-    /* Wrap MPI error codes by RSA check failure error code */
-    if( ret != 0 && ret != MBEDTLS_ERR_RSA_KEY_CHECK_FAILED )
-    {
-        ret += MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
-    }
-
-    return( ret );
-}
-
-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 )
-{
-    int ret = 0;
-    mbedtls_mpi K;
-    mbedtls_mpi_init( &K );
-
-    /* DP = D mod P-1 */
-    if( DP != NULL )
-    {
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, P, 1  ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( DP, D, &K ) );
-    }
-
-    /* DQ = D mod Q-1 */
-    if( DQ != NULL )
-    {
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, Q, 1  ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( DQ, D, &K ) );
-    }
-
-    /* QP = Q^{-1} mod P */
-    if( QP != NULL )
-    {
-        MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( QP, Q, P ) );
-    }
-
-cleanup:
-    mbedtls_mpi_free( &K );
-
-    return( ret );
-}
-
-
-/*
- * Default RSA interface implementation
- */
-
-#if !defined(MBEDTLS_RSA_ALT)
-
 int mbedtls_rsa_import( mbedtls_rsa_context *ctx,
                         const mbedtls_mpi *N,
                         const mbedtls_mpi *P, const mbedtls_mpi *Q,
diff --git a/library/rsa_internal.c b/library/rsa_internal.c
new file mode 100644
index 0000000..879e2d5
--- /dev/null
+++ b/library/rsa_internal.c
@@ -0,0 +1,471 @@
+/*
+ *  Helper functions for the RSA module
+ *
+ *  Copyright (C) 2006-2017, ARM Limited, All Rights Reserved
+ *  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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ *
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_RSA_C)
+
+#include "mbedtls/rsa.h"
+#include "mbedtls/bignum.h"
+#include "mbedtls/rsa_internal.h"
+
+/*
+ * Compute RSA prime factors from public and private exponents
+ *
+ * Summary of algorithm:
+ * Setting F := lcm(P-1,Q-1), the idea is as follows:
+ *
+ * (a) For any 1 <= X < N with gcd(X,N)=1, we have X^F = 1 modulo N, so X^(F/2)
+ *     is a square root of 1 in Z/NZ. Since Z/NZ ~= Z/PZ x Z/QZ by CRT and the
+ *     square roots of 1 in Z/PZ and Z/QZ are +1 and -1, this leaves the four
+ *     possibilities X^(F/2) = (+-1, +-1). If it happens that X^(F/2) = (-1,+1)
+ *     or (+1,-1), then gcd(X^(F/2) + 1, N) will be equal to one of the prime
+ *     factors of N.
+ *
+ * (b) If we don't know F/2 but (F/2) * K for some odd (!) K, then the same
+ *     construction still applies since (-)^K is the identity on the set of
+ *     roots of 1 in Z/NZ.
+ *
+ * The public and private key primitives (-)^E and (-)^D are mutually inverse
+ * bijections on Z/NZ if and only if (-)^(DE) is the identity on Z/NZ, i.e.
+ * if and only if DE - 1 is a multiple of F, say DE - 1 = F * L.
+ * Splitting L = 2^t * K with K odd, we have
+ *
+ *   DE - 1 = FL = (F/2) * (2^(t+1)) * K,
+ *
+ * so (F / 2) * K is among the numbers
+ *
+ *   (DE - 1) >> 1, (DE - 1) >> 2, ..., (DE - 1) >> ord
+ *
+ * where ord is the order of 2 in (DE - 1).
+ * We can therefore iterate through these numbers apply the construction
+ * of (a) and (b) above to attempt to factor N.
+ *
+ */
+int mbedtls_rsa_deduce_primes( mbedtls_mpi const *N,
+                     mbedtls_mpi const *D, mbedtls_mpi const *E,
+                     mbedtls_mpi *P, mbedtls_mpi *Q )
+{
+    int ret = 0;
+
+    uint16_t attempt;  /* Number of current attempt  */
+    uint16_t iter;     /* Number of squares computed in the current attempt */
+
+    uint16_t order;    /* Order of 2 in DE - 1 */
+
+    mbedtls_mpi T;  /* Holds largest odd divisor of DE - 1     */
+    mbedtls_mpi K;  /* Temporary holding the current candidate */
+
+    const unsigned int primes[] = { 2,
+           3,    5,    7,   11,   13,   17,   19,   23,
+          29,   31,   37,   41,   43,   47,   53,   59,
+          61,   67,   71,   73,   79,   83,   89,   97,
+         101,  103,  107,  109,  113,  127,  131,  137,
+         139,  149,  151,  157,  163,  167,  173,  179,
+         181,  191,  193,  197,  199,  211,  223,  227,
+         229,  233,  239,  241,  251,  257,  263,  269,
+         271,  277,  281,  283,  293,  307,  311,  313
+    };
+
+    const size_t num_primes = sizeof( primes ) / sizeof( *primes );
+
+    if( P == NULL || Q == NULL || P->p != NULL || Q->p != NULL )
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+
+    if( mbedtls_mpi_cmp_int( N, 0 ) <= 0 ||
+        mbedtls_mpi_cmp_int( D, 1 ) <= 0 ||
+        mbedtls_mpi_cmp_mpi( D, N ) >= 0 ||
+        mbedtls_mpi_cmp_int( E, 1 ) <= 0 ||
+        mbedtls_mpi_cmp_mpi( E, N ) >= 0 )
+    {
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+    }
+
+    /*
+     * Initializations and temporary changes
+     */
+
+    mbedtls_mpi_init( &K );
+    mbedtls_mpi_init( &T );
+
+    /* T := DE - 1 */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T, D,  E ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &T, &T, 1 ) );
+
+    if( ( order = mbedtls_mpi_lsb( &T ) ) == 0 )
+    {
+        ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
+        goto cleanup;
+    }
+
+    /* After this operation, T holds the largest odd divisor of DE - 1. */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &T, order ) );
+
+    /*
+     * Actual work
+     */
+
+    /* Skip trying 2 if N == 1 mod 8 */
+    attempt = 0;
+    if( N->p[0] % 8 == 1 )
+        attempt = 1;
+
+    for( ; attempt < num_primes; ++attempt )
+    {
+        mbedtls_mpi_lset( &K, primes[attempt] );
+
+        /* Check if gcd(K,N) = 1 */
+        MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( P, &K, N ) );
+        if( mbedtls_mpi_cmp_int( P, 1 ) != 0 )
+            continue;
+
+        /* Go through K^T + 1, K^(2T) + 1, K^(4T) + 1, ...
+         * and check whether they have nontrivial GCD with N. */
+        MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &K, &K, &T, N,
+                             Q /* temporarily use Q for storing Montgomery
+                                * multiplication helper values */ ) );
+
+        for( iter = 1; iter < order; ++iter )
+        {
+            MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( &K, &K, 1 ) );
+            MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( P, &K, N ) );
+
+            if( mbedtls_mpi_cmp_int( P, 1 ) ==  1 &&
+                mbedtls_mpi_cmp_mpi( P, N ) == -1 )
+            {
+                /*
+                 * Have found a nontrivial divisor P of N.
+                 * Set Q := N / P.
+                 */
+
+                MBEDTLS_MPI_CHK( mbedtls_mpi_div_mpi( Q, NULL, N, P ) );
+                goto cleanup;
+            }
+
+            MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, &K, 1 ) );
+            MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, &K, &K ) );
+            MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &K, &K, N ) );
+        }
+    }
+
+    ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
+
+cleanup:
+
+    mbedtls_mpi_free( &K );
+    mbedtls_mpi_free( &T );
+    return( ret );
+}
+
+/*
+ * Given P, Q and the public exponent E, deduce D.
+ * This is essentially a modular inversion.
+ */
+int mbedtls_rsa_deduce_private_exponent( mbedtls_mpi const *P,
+                                         mbedtls_mpi const *Q,
+                                         mbedtls_mpi const *E,
+                                         mbedtls_mpi *D )
+{
+    int ret = 0;
+    mbedtls_mpi K, L;
+
+    if( D == NULL || mbedtls_mpi_cmp_int( D, 0 ) != 0 )
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+
+    if( mbedtls_mpi_cmp_int( P, 1 ) <= 0 ||
+        mbedtls_mpi_cmp_int( Q, 1 ) <= 0 ||
+        mbedtls_mpi_cmp_int( E, 0 ) == 0 )
+    {
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+    }
+
+    mbedtls_mpi_init( &K );
+    mbedtls_mpi_init( &L );
+
+    /* Temporarily put K := P-1 and L := Q-1 */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, P, 1 ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &L, Q, 1 ) );
+
+    /* Temporarily put D := gcd(P-1, Q-1) */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( D, &K, &L ) );
+
+    /* K := LCM(P-1, Q-1) */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, &K, &L ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_div_mpi( &K, NULL, &K, D ) );
+
+    /* Compute modular inverse of E in LCM(P-1, Q-1) */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( D, E, &K ) );
+
+cleanup:
+
+    mbedtls_mpi_free( &K );
+    mbedtls_mpi_free( &L );
+
+    return( ret );
+}
+
+/*
+ * Check that RSA CRT parameters are in accordance with core parameters.
+ */
+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 )
+{
+    int ret = 0;
+
+    mbedtls_mpi K, L;
+    mbedtls_mpi_init( &K );
+    mbedtls_mpi_init( &L );
+
+    /* Check that DP - D == 0 mod P - 1 */
+    if( DP != NULL )
+    {
+        if( P == NULL )
+        {
+            ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
+            goto cleanup;
+        }
+
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, P, 1 ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &L, DP, D ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &L, &L, &K ) );
+
+        if( mbedtls_mpi_cmp_int( &L, 0 ) != 0 )
+        {
+            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+            goto cleanup;
+        }
+    }
+
+    /* Check that DQ - D == 0 mod Q - 1 */
+    if( DQ != NULL )
+    {
+        if( Q == NULL )
+        {
+            ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
+            goto cleanup;
+        }
+
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, Q, 1 ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &L, DQ, D ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &L, &L, &K ) );
+
+        if( mbedtls_mpi_cmp_int( &L, 0 ) != 0 )
+        {
+            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+            goto cleanup;
+        }
+    }
+
+    /* Check that QP * Q - 1 == 0 mod P */
+    if( QP != NULL )
+    {
+        if( P == NULL || Q == NULL )
+        {
+            ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
+            goto cleanup;
+        }
+
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, QP, Q ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, &K, 1 ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &K, &K, P ) );
+        if( mbedtls_mpi_cmp_int( &K, 0 ) != 0 )
+        {
+            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+            goto cleanup;
+        }
+    }
+
+cleanup:
+
+    /* Wrap MPI error codes by RSA check failure error code */
+    if( ret != 0 &&
+        ret != MBEDTLS_ERR_RSA_KEY_CHECK_FAILED &&
+        ret != MBEDTLS_ERR_RSA_BAD_INPUT_DATA )
+    {
+        ret += MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+    }
+
+    mbedtls_mpi_free( &K );
+    mbedtls_mpi_free( &L );
+
+    return( ret );
+}
+
+/*
+ * Check that core RSA parameters are sane.
+ */
+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 )
+{
+    int ret = 0;
+    mbedtls_mpi K, L;
+
+    mbedtls_mpi_init( &K );
+    mbedtls_mpi_init( &L );
+
+    /*
+     * Step 1: If PRNG provided, check that P and Q are prime
+     */
+
+#if defined(MBEDTLS_GENPRIME)
+    if( f_rng != NULL && P != NULL &&
+        ( ret = mbedtls_mpi_is_prime( P, f_rng, p_rng ) ) != 0 )
+    {
+        ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+        goto cleanup;
+    }
+
+    if( f_rng != NULL && Q != NULL &&
+        ( ret = mbedtls_mpi_is_prime( Q, f_rng, p_rng ) ) != 0 )
+    {
+        ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+        goto cleanup;
+    }
+#else
+    ((void) f_rng);
+    ((void) p_rng);
+#endif /* MBEDTLS_GENPRIME */
+
+    /*
+     * Step 2: Check that 1 < N = PQ
+     */
+
+    if( P != NULL && Q != NULL && N != NULL )
+    {
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, P, Q ) );
+        if( mbedtls_mpi_cmp_int( N, 1 )  <= 0 ||
+            mbedtls_mpi_cmp_mpi( &K, N ) != 0 )
+        {
+            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+            goto cleanup;
+        }
+    }
+
+    /*
+     * Step 3: Check and 1 < D, E < N if present.
+     */
+
+    if( N != NULL && D != NULL && E != NULL )
+    {
+        if ( mbedtls_mpi_cmp_int( D, 1 ) <= 0 ||
+             mbedtls_mpi_cmp_int( E, 1 ) <= 0 ||
+             mbedtls_mpi_cmp_mpi( D, N ) >= 0 ||
+             mbedtls_mpi_cmp_mpi( E, N ) >= 0 )
+        {
+            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+            goto cleanup;
+        }
+    }
+
+    /*
+     * Step 4: Check that D, E are inverse modulo P-1 and Q-1
+     */
+
+    if( P != NULL && Q != NULL && D != NULL && E != NULL )
+    {
+        if( mbedtls_mpi_cmp_int( P, 1 ) <= 0 ||
+            mbedtls_mpi_cmp_int( Q, 1 ) <= 0 )
+        {
+            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+            goto cleanup;
+        }
+
+        /* Compute DE-1 mod P-1 */
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, D, E ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, &K, 1 ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &L, P, 1 ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &K, &K, &L ) );
+        if( mbedtls_mpi_cmp_int( &K, 0 ) != 0 )
+        {
+            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+            goto cleanup;
+        }
+
+        /* Compute DE-1 mod Q-1 */
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &K, D, E ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, &K, 1 ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &L, Q, 1 ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &K, &K, &L ) );
+        if( mbedtls_mpi_cmp_int( &K, 0 ) != 0 )
+        {
+            ret = MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+            goto cleanup;
+        }
+    }
+
+cleanup:
+
+    mbedtls_mpi_free( &K );
+    mbedtls_mpi_free( &L );
+
+    /* Wrap MPI error codes by RSA check failure error code */
+    if( ret != 0 && ret != MBEDTLS_ERR_RSA_KEY_CHECK_FAILED )
+    {
+        ret += MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
+    }
+
+    return( ret );
+}
+
+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 )
+{
+    int ret = 0;
+    mbedtls_mpi K;
+    mbedtls_mpi_init( &K );
+
+    /* DP = D mod P-1 */
+    if( DP != NULL )
+    {
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, P, 1  ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( DP, D, &K ) );
+    }
+
+    /* DQ = D mod Q-1 */
+    if( DQ != NULL )
+    {
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &K, Q, 1  ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( DQ, D, &K ) );
+    }
+
+    /* QP = Q^{-1} mod P */
+    if( QP != NULL )
+    {
+        MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( QP, Q, P ) );
+    }
+
+cleanup:
+    mbedtls_mpi_free( &K );
+
+    return( ret );
+}
+
+#endif /* MBEDTLS_RSA_C */
diff --git a/tests/suites/test_suite_rsa.function b/tests/suites/test_suite_rsa.function
index 9ee8ea1..3f892f7 100644
--- a/tests/suites/test_suite_rsa.function
+++ b/tests/suites/test_suite_rsa.function
@@ -1,5 +1,6 @@
 /* BEGIN_HEADER */
 #include "mbedtls/rsa.h"
+#include "mbedtls/rsa_internal.h"
 #include "mbedtls/md2.h"
 #include "mbedtls/md4.h"
 #include "mbedtls/md5.h"