include/polarssl/rsa.h

/**
 * \file rsa.h
 *
 * \brief The RSA public-key cryptosystem
 *
 *  Copyright (C) 2006-2010, Brainspark B.V.
 *
 *  This file is part of PolarSSL (http://www.polarssl.org)
 *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
 *
 *  All rights reserved.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#ifndef POLARSSL_RSA_H
#define POLARSSL_RSA_H

#include "bignum.h"

/*
 * RSA Error codes
 */
#define POLARSSL_ERR_RSA_BAD_INPUT_DATA                    -0x4080  /**< Bad input parameters to function. */
#define POLARSSL_ERR_RSA_INVALID_PADDING                   -0x4100  /**< Input data contains invalid padding and is rejected. */
#define POLARSSL_ERR_RSA_KEY_GEN_FAILED                    -0x4180  /**< Something failed during generation of a key. */
#define POLARSSL_ERR_RSA_KEY_CHECK_FAILED                  -0x4200  /**< Key failed to pass the libraries validity check. */
#define POLARSSL_ERR_RSA_PUBLIC_FAILED                     -0x4280  /**< The public key operation failed. */
#define POLARSSL_ERR_RSA_PRIVATE_FAILED                    -0x4300  /**< The private key operation failed. */
#define POLARSSL_ERR_RSA_VERIFY_FAILED                     -0x4380  /**< The PKCS#1 verification failed. */
#define POLARSSL_ERR_RSA_OUTPUT_TOO_LARGE                  -0x4400  /**< The output buffer for decryption is not large enough. */
#define POLARSSL_ERR_RSA_RNG_FAILED                        -0x4480  /**< The random generator failed to generate non-zeros. */

/*
 * PKCS#1 constants
 */
#define SIG_RSA_RAW     0
#define SIG_RSA_MD2     2
#define SIG_RSA_MD4     3
#define SIG_RSA_MD5     4
#define SIG_RSA_SHA1    5
#define SIG_RSA_SHA224 14
#define SIG_RSA_SHA256 11
#define SIG_RSA_SHA384 12
#define SIG_RSA_SHA512 13

#define RSA_PUBLIC      0
#define RSA_PRIVATE     1

#define RSA_PKCS_V15    0
#define RSA_PKCS_V21    1

#define RSA_SIGN        1
#define RSA_CRYPT       2

#define ASN1_STR_CONSTRUCTED_SEQUENCE   "\x30"
#define ASN1_STR_NULL                   "\x05"
#define ASN1_STR_OID                    "\x06"
#define ASN1_STR_OCTET_STRING           "\x04"

#define OID_DIGEST_ALG_MDX              "\x2A\x86\x48\x86\xF7\x0D\x02\x00"
#define OID_HASH_ALG_SHA1               "\x2b\x0e\x03\x02\x1a"
#define OID_HASH_ALG_SHA2X              "\x60\x86\x48\x01\x65\x03\x04\x02\x00"

#define OID_ISO_MEMBER_BODIES           "\x2a"
#define OID_ISO_IDENTIFIED_ORG          "\x2b"

/*
 * ISO Member bodies OID parts
 */
#define OID_COUNTRY_US                  "\x86\x48"
#define OID_RSA_DATA_SECURITY           "\x86\xf7\x0d"

/*
 * ISO Identified organization OID parts
 */
#define OID_OIW_SECSIG_SHA1             "\x0e\x03\x02\x1a"

/*
 * DigestInfo ::= SEQUENCE {
 *   digestAlgorithm DigestAlgorithmIdentifier,
 *   digest Digest }
 *
 * DigestAlgorithmIdentifier ::= AlgorithmIdentifier
 *
 * Digest ::= OCTET STRING
 */
#define ASN1_HASH_MDX                           \
(                                               \
    ASN1_STR_CONSTRUCTED_SEQUENCE "\x20"        \
      ASN1_STR_CONSTRUCTED_SEQUENCE "\x0C"      \
        ASN1_STR_OID "\x08"                     \
      OID_DIGEST_ALG_MDX                        \
    ASN1_STR_NULL "\x00"                        \
      ASN1_STR_OCTET_STRING "\x10"              \
)

#define ASN1_HASH_SHA1                          \
    ASN1_STR_CONSTRUCTED_SEQUENCE "\x21"        \
      ASN1_STR_CONSTRUCTED_SEQUENCE "\x09"      \
        ASN1_STR_OID "\x05"                     \
      OID_HASH_ALG_SHA1                         \
        ASN1_STR_NULL "\x00"                    \
      ASN1_STR_OCTET_STRING "\x14"

#define ASN1_HASH_SHA1_ALT                      \
    ASN1_STR_CONSTRUCTED_SEQUENCE "\x1F"        \
      ASN1_STR_CONSTRUCTED_SEQUENCE "\x07"      \
        ASN1_STR_OID "\x05"                     \
      OID_HASH_ALG_SHA1                         \
      ASN1_STR_OCTET_STRING "\x14"

#define ASN1_HASH_SHA2X                         \
    ASN1_STR_CONSTRUCTED_SEQUENCE "\x11"        \
      ASN1_STR_CONSTRUCTED_SEQUENCE "\x0d"      \
        ASN1_STR_OID "\x09"                     \
      OID_HASH_ALG_SHA2X                        \
        ASN1_STR_NULL "\x00"                    \
      ASN1_STR_OCTET_STRING "\x00"

/**
 * \brief          RSA context structure
 */
typedef struct
{
    int ver;                    /*!<  always 0          */
    size_t len;                 /*!<  size(N) in chars  */

    mpi N;                      /*!<  public modulus    */
    mpi E;                      /*!<  public exponent   */

    mpi D;                      /*!<  private exponent  */
    mpi P;                      /*!<  1st prime factor  */
    mpi Q;                      /*!<  2nd prime factor  */
    mpi DP;                     /*!<  D % (P - 1)       */
    mpi DQ;                     /*!<  D % (Q - 1)       */
    mpi QP;                     /*!<  1 / (Q % P)       */

    mpi RN;                     /*!<  cached R^2 mod N  */
    mpi RP;                     /*!<  cached R^2 mod P  */
    mpi RQ;                     /*!<  cached R^2 mod Q  */

#if !defined(POLARSSL_RSA_NO_CRT)
    mpi Vi;                     /*!<  cached blinding value     */
    mpi Vf;                     /*!<  cached un-blinding value  */
#endif

    int padding;                /*!<  RSA_PKCS_V15 for 1.5 padding and
                                      RSA_PKCS_v21 for OAEP/PSS         */
    int hash_id;                /*!<  Hash identifier of md_type_t as
                                      specified in the md.h header file
                                      for the EME-OAEP and EMSA-PSS
                                      encoding                          */
}
rsa_context;

#ifdef __cplusplus
extern "C" {
#endif

/**
 * \brief          Initialize an RSA context
 *
 *                 Note: Set padding to RSA_PKCS_V21 for the RSAES-OAEP
 *                 encryption scheme and the RSASSA-PSS signature scheme.
 *
 * \param ctx      RSA context to be initialized
 * \param padding  RSA_PKCS_V15 or RSA_PKCS_V21
 * \param hash_id  RSA_PKCS_V21 hash identifier
 *
 * \note           The hash_id parameter is actually ignored
 *                 when using RSA_PKCS_V15 padding.
 */
void rsa_init( rsa_context *ctx,
               int padding,
               int hash_id);

/**
 * \brief          Generate an RSA keypair
 *
 * \param ctx      RSA context that will hold the key
 * \param f_rng    RNG function
 * \param p_rng    RNG parameter
 * \param nbits    size of the public key in bits
 * \param exponent public exponent (e.g., 65537)
 *
 * \note           rsa_init() must be called beforehand to setup
 *                 the RSA context.
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 */
int rsa_gen_key( rsa_context *ctx,
                 int (*f_rng)(void *, unsigned char *, size_t),
                 void *p_rng,
                 unsigned int nbits, int exponent );

/**
 * \brief          Check a public RSA key
 *
 * \param ctx      RSA context to be checked
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 */
int rsa_check_pubkey( const rsa_context *ctx );

/**
 * \brief          Check a private RSA key
 *
 * \param ctx      RSA context to be checked
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 */
int rsa_check_privkey( const rsa_context *ctx );

/**
 * \brief          Do an RSA public key operation
 *
 * \param ctx      RSA context
 * \param input    input buffer
 * \param output   output buffer
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           This function does NOT take care of message
 *                 padding. Also, be sure to set input[0] = 0 or assure that
 *                 input is smaller than N.
 *
 * \note           The input and output buffers must be large
 *                 enough (eg. 128 bytes if RSA-1024 is used).
 */
int rsa_public( rsa_context *ctx,
                const unsigned char *input,
                unsigned char *output );

/**
 * \brief          Do an RSA private key operation
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Needed for blinding)
 * \param p_rng    RNG parameter
 * \param input    input buffer
 * \param output   output buffer
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The input and output buffers must be large
 *                 enough (eg. 128 bytes if RSA-1024 is used).
 */
int rsa_private( rsa_context *ctx,
                 int (*f_rng)(void *, unsigned char *, size_t),
                 void *p_rng,
                 const unsigned char *input,
                 unsigned char *output );

/**
 * \brief          Generic wrapper to perform a PKCS#1 encryption using the
 *                 mode from the context. Add the message padding, then do an
 *                 RSA operation.
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Needed for padding and PKCS#1 v2.1 encoding
 *                               and RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param ilen     contains the plaintext length
 * \param input    buffer holding the data to be encrypted
 * \param output   buffer that will hold the ciphertext
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The output buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 */
int rsa_pkcs1_encrypt( rsa_context *ctx,
                       int (*f_rng)(void *, unsigned char *, size_t),
                       void *p_rng,
                       int mode, size_t ilen,
                       const unsigned char *input,
                       unsigned char *output );

/**
 * \brief          Perform a PKCS#1 v1.5 encryption (RSAES-PKCS1-v1_5-ENCRYPT)
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Needed for padding and RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param ilen     contains the plaintext length
 * \param input    buffer holding the data to be encrypted
 * \param output   buffer that will hold the ciphertext
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The output buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 */
int rsa_rsaes_pkcs1_v15_encrypt( rsa_context *ctx,
                                 int (*f_rng)(void *, unsigned char *, size_t),
                                 void *p_rng,
                                 int mode, size_t ilen,
                                 const unsigned char *input,
                                 unsigned char *output );

/**
 * \brief          Perform a PKCS#1 v2.1 OAEP encryption (RSAES-OAEP-ENCRYPT)
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Needed for padding and PKCS#1 v2.1 encoding
 *                               and RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param label    buffer holding the custom label to use
 * \param label_len contains the label length
 * \param ilen     contains the plaintext length
 * \param input    buffer holding the data to be encrypted
 * \param output   buffer that will hold the ciphertext
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The output buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 */
int rsa_rsaes_oaep_encrypt( rsa_context *ctx,
                            int (*f_rng)(void *, unsigned char *, size_t),
                            void *p_rng,
                            int mode,
                            const unsigned char *label, size_t label_len,
                            size_t ilen,
                            const unsigned char *input,
                            unsigned char *output );

/**
 * \brief          Generic wrapper to perform a PKCS#1 decryption using the
 *                 mode from the context. Do an RSA operation, then remove
 *                 the message padding
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Only needed for RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param olen     will contain the plaintext length
 * \param input    buffer holding the encrypted data
 * \param output   buffer that will hold the plaintext
 * \param output_max_len    maximum length of the output buffer
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The output buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used) otherwise
 *                 an error is thrown.
 */
int rsa_pkcs1_decrypt( rsa_context *ctx,
                       int (*f_rng)(void *, unsigned char *, size_t),
                       void *p_rng,
                       int mode, size_t *olen,
                       const unsigned char *input,
                       unsigned char *output,
                       size_t output_max_len );

/**
 * \brief          Perform a PKCS#1 v1.5 decryption (RSAES-PKCS1-v1_5-DECRYPT)
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Only needed for RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param olen     will contain the plaintext length
 * \param input    buffer holding the encrypted data
 * \param output   buffer that will hold the plaintext
 * \param output_max_len    maximum length of the output buffer
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The output buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used) otherwise
 *                 an error is thrown.
 */
int rsa_rsaes_pkcs1_v15_decrypt( rsa_context *ctx,
                                 int (*f_rng)(void *, unsigned char *, size_t),
                                 void *p_rng,
                                 int mode, size_t *olen,
                                 const unsigned char *input,
                                 unsigned char *output,
                                 size_t output_max_len );

/**
 * \brief          Perform a PKCS#1 v2.1 OAEP decryption (RSAES-OAEP-DECRYPT)
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Only needed for RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param label    buffer holding the custom label to use
 * \param label_len contains the label length
 * \param olen     will contain the plaintext length
 * \param input    buffer holding the encrypted data
 * \param output   buffer that will hold the plaintext
 * \param output_max_len    maximum length of the output buffer
 *
 * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The output buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used) otherwise
 *                 an error is thrown.
 */
int rsa_rsaes_oaep_decrypt( rsa_context *ctx,
                            int (*f_rng)(void *, unsigned char *, size_t),
                            void *p_rng,
                            int mode,
                            const unsigned char *label, size_t label_len,
                            size_t *olen,
                            const unsigned char *input,
                            unsigned char *output,
                            size_t output_max_len );

/**
 * \brief          Generic wrapper to perform a PKCS#1 signature using the
 *                 mode from the context. Do a private RSA operation to sign
 *                 a message digest
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Needed for PKCS#1 v2.1 encoding and for
 *                 RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param hash_id  SIG_RSA_RAW, SIG_RSA_MD{2,4,5} or SIG_RSA_SHA{1,224,256,384,512}
 * \param hashlen  message digest length (for SIG_RSA_RAW only)
 * \param hash     buffer holding the message digest
 * \param sig      buffer that will hold the ciphertext
 *
 * \return         0 if the signing operation was successful,
 *                 or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The "sig" buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 *
 * \note           In case of PKCS#1 v2.1 encoding keep in mind that
 *                 the hash_id in the RSA context is the one used for the
 *                 encoding. hash_id in the function call is the type of hash
 *                 that is encoded. According to RFC 3447 it is advised to
 *                 keep both hashes the same.
 */
int rsa_pkcs1_sign( rsa_context *ctx,
                    int (*f_rng)(void *, unsigned char *, size_t),
                    void *p_rng,
                    int mode,
                    int hash_id,
                    unsigned int hashlen,
                    const unsigned char *hash,
                    unsigned char *sig );

/**
 * \brief          Perform a PKCS#1 v1.5 signature (RSASSA-PKCS1-v1_5-SIGN)
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Only needed for RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param hash_id  SIG_RSA_RAW, SIG_RSA_MD{2,4,5} or SIG_RSA_SHA{1,224,256,384,512}
 * \param hashlen  message digest length (for SIG_RSA_RAW only)
 * \param hash     buffer holding the message digest
 * \param sig      buffer that will hold the ciphertext
 *
 * \return         0 if the signing operation was successful,
 *                 or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The "sig" buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 */
int rsa_rsassa_pkcs1_v15_sign( rsa_context *ctx,
                               int (*f_rng)(void *, unsigned char *, size_t),
                               void *p_rng,
                               int mode,
                               int hash_id,
                               unsigned int hashlen,
                               const unsigned char *hash,
                               unsigned char *sig );

/**
 * \brief          Perform a PKCS#1 v2.1 PSS signature (RSASSA-PSS-SIGN)
 *
 * \param ctx      RSA context
 * \param f_rng    RNG function (Needed for PKCS#1 v2.1 encoding and for
 *                               RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param hash_id  SIG_RSA_RAW, SIG_RSA_MD{2,4,5} or SIG_RSA_SHA{1,224,256,384,512}
 * \param hashlen  message digest length (for SIG_RSA_RAW only)
 * \param hash     buffer holding the message digest
 * \param sig      buffer that will hold the ciphertext
 *
 * \return         0 if the signing operation was successful,
 *                 or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The "sig" buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 *
 * \note           In case of PKCS#1 v2.1 encoding keep in mind that
 *                 the hash_id in the RSA context is the one used for the
 *                 encoding. hash_id in the function call is the type of hash
 *                 that is encoded. According to RFC 3447 it is advised to
 *                 keep both hashes the same.
 */
int rsa_rsassa_pss_sign( rsa_context *ctx,
                         int (*f_rng)(void *, unsigned char *, size_t),
                         void *p_rng,
                         int mode,
                         int hash_id,
                         unsigned int hashlen,
                         const unsigned char *hash,
                         unsigned char *sig );

/**
 * \brief          Generic wrapper to perform a PKCS#1 verification using the
 *                 mode from the context. Do a public RSA operation and check
 *                 the message digest
 *
 * \param ctx      points to an RSA public key
 * \param f_rng    RNG function (Only needed for RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param hash_id  SIG_RSA_RAW, SIG_RSA_MD{2,4,5} or SIG_RSA_SHA{1,224,256,384,512}
 * \param hashlen  message digest length (for SIG_RSA_RAW only)
 * \param hash     buffer holding the message digest
 * \param sig      buffer holding the ciphertext
 *
 * \return         0 if the verify operation was successful,
 *                 or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The "sig" buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 *
 * \note           In case of PKCS#1 v2.1 encoding keep in mind that
 *                 the hash_id in the RSA context is the one used for the
 *                 verification. hash_id in the function call is the type of hash
 *                 that is verified. According to RFC 3447 it is advised to
 *                 keep both hashes the same.
 */
int rsa_pkcs1_verify( rsa_context *ctx,
                      int (*f_rng)(void *, unsigned char *, size_t),
                      void *p_rng,
                      int mode,
                      int hash_id,
                      unsigned int hashlen,
                      const unsigned char *hash,
                      unsigned char *sig );

/**
 * \brief          Perform a PKCS#1 v1.5 verification (RSASSA-PKCS1-v1_5-VERIFY)
 *
 * \param ctx      points to an RSA public key
 * \param f_rng    RNG function (Only needed for RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param hash_id  SIG_RSA_RAW, SIG_RSA_MD{2,4,5} or SIG_RSA_SHA{1,224,256,384,512}
 * \param hashlen  message digest length (for SIG_RSA_RAW only)
 * \param hash     buffer holding the message digest
 * \param sig      buffer holding the ciphertext
 *
 * \return         0 if the verify operation was successful,
 *                 or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The "sig" buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 */
int rsa_rsassa_pkcs1_v15_verify( rsa_context *ctx,
                                 int (*f_rng)(void *, unsigned char *, size_t),
                                 void *p_rng,
                                 int mode,
                                 int hash_id,
                                 unsigned int hashlen,
                                 const unsigned char *hash,
                                 unsigned char *sig );

/**
 * \brief          Perform a PKCS#1 v2.1 PSS verification (RSASSA-PSS-VERIFY)
 * \brief          Do a public RSA and check the message digest
 *
 * \param ctx      points to an RSA public key
 * \param f_rng    RNG function (Only needed for RSA_PRIVATE)
 * \param p_rng    RNG parameter
 * \param mode     RSA_PUBLIC or RSA_PRIVATE
 * \param hash_id  SIG_RSA_RAW, SIG_RSA_MD{2,4,5} or SIG_RSA_SHA{1,224,256,384,512}
 * \param hashlen  message digest length (for SIG_RSA_RAW only)
 * \param hash     buffer holding the message digest
 * \param sig      buffer holding the ciphertext
 *
 * \return         0 if the verify operation was successful,
 *                 or an POLARSSL_ERR_RSA_XXX error code
 *
 * \note           The "sig" buffer must be as large as the size
 *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
 *
 * \note           In case of PKCS#1 v2.1 encoding keep in mind that
 *                 the hash_id in the RSA context is the one used for the
 *                 verification. hash_id in the function call is the type of hash
 *                 that is verified. According to RFC 3447 it is advised to
 *                 keep both hashes the same.
 */
int rsa_rsassa_pss_verify( rsa_context *ctx,
                           int (*f_rng)(void *, unsigned char *, size_t),
                           void *p_rng,
                           int mode,
                           int hash_id,
                           unsigned int hashlen,
                           const unsigned char *hash,
                           unsigned char *sig );

/**
 * \brief          Free the components of an RSA key
 *
 * \param ctx      RSA Context to free
 */
void rsa_free( rsa_context *ctx );

/**
 * \brief          Checkup routine
 *
 * \return         0 if successful, or 1 if the test failed
 */
int rsa_self_test( int verbose );

#ifdef __cplusplus
}
#endif

#endif /* rsa.h */