使用Libtomcrypt RSA/ECC等加密算法到项目中

绝地灬酷狼 2022-08-05 00:51 244阅读 0赞

LibTomCrypt是一个非常不错的加解密开源库,支持C/C++编译,可以支持跨平台.更详细的信息请参考其官网:[http://www.libtom.net/][http_www.libtom.net]

一、材料准备

1、libtomcrypt

2、libtommath

二、将项目增加到自己的项目工程中

以IAR为例子,直接上图片.

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另外include路径按照自己项目存放的文件夹路径进行放置,以下是我自己的目录引用情况

$PROJ\_DIR$\\..\\libtomcrypt\\src\\headers  
$PROJ\_DIR$\\..\\libtommath

三、修改代码

由于该文件用的是跨平台的,所以部分算法可能需要进行修改.例如,随机数产生.如果自己的芯片支持,则可以考虑使用芯片的随机数发生器进行产生随机数。

四、增加宏控制

在 tomcrypt\_custom.h文件夹配置相关宏,用于控制其编译

如,在IAR中增加宏控制

LTC_EASY
    _CRT_SECURE_NO_WARNINGS
    LTC_SOURCE
    LTM_DESC

五、开始使用库函数

在main.C中引用tomcrypt.h头文件

#include <tomcrypt.h>

六、修改tomcrypt\_pk.h文件,使用 LTC\_LTC\_PKCS\_1\_V1\_5 进行加解密 相关部分为

/* These use LTC_PKCS #1 v2.0 padding */
    #define rsa_encrypt_key(_in, _inlen, _out, _outlen, _lparam, _lparamlen, _prng, _prng_idx, _hash_idx, _key) \
      rsa_encrypt_key_ex(_in, _inlen, _out, _outlen, _lparam, _lparamlen, _prng, _prng_idx, _hash_idx, LTC_LTC_PKCS_1_V1_5, _key)
    
    #define rsa_decrypt_key(_in, _inlen, _out, _outlen, _lparam, _lparamlen, _hash_idx, _stat, _key) \
      rsa_decrypt_key_ex(_in, _inlen, _out, _outlen, _lparam, _lparamlen, _hash_idx, LTC_LTC_PKCS_1_V1_5, _stat, _key)

七、修改LTC\_LTC\_PKCS\_1\_V1\_5后,需要修改pkcs\_1\_v1\_5\_encode.c文件的pkcs\_1\_v1\_5\_encode函数,使其随机数产生器使用MCU硬件产生.

如,我修改后的代码

/* LibTomCrypt, modular cryptographic library -- Tom St Denis
     *
     * LibTomCrypt is a library that provides various cryptographic
     * algorithms in a highly modular and flexible manner.
     *
     * The library is free for all purposes without any express
     * guarantee it works.
     *
     * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
     */
    #include "tomcrypt.h"
    #include "security.h"
    /*! \file pkcs_1_v1_5_encode.c
     *
     *  LTC_PKCS #1 v1.5 Padding (Andreas Lange)
     */
    
    #ifdef LTC_PKCS_1
    
    /*! \brief LTC_PKCS #1 v1.5 encode.
     *
     *  \param msg              The data to encode
     *  \param msglen           The length of the data to encode (octets)
     *  \param block_type       Block type to use in padding (\sa ltc_pkcs_1_v1_5_blocks)
     *  \param modulus_bitlen   The bit length of the RSA modulus
     *  \param prng             An active PRNG state (only for LTC_LTC_PKCS_1_EME)
     *  \param prng_idx         The index of the PRNG desired (only for LTC_LTC_PKCS_1_EME)
     *  \param out              [out] The destination for the encoded data
     *  \param outlen           [in/out] The max size and resulting size of the encoded data
     *
     *  \return CRYPT_OK if successful
     */
    int pkcs_1_v1_5_encode(const unsigned char *msg, 
                                 unsigned long  msglen,
                                           int  block_type,
                                 unsigned long  modulus_bitlen,
                                    prng_state *prng, 
                                           int  prng_idx,
                                 unsigned char *out, 
                                 unsigned long *outlen)
    {
      unsigned long modulus_len, ps_len, i;
      unsigned char *ps;
      int result;
    
      /* valid block_type? */
      if ((block_type != LTC_LTC_PKCS_1_EMSA) &&
          (block_type != LTC_LTC_PKCS_1_EME)) {
         return CRYPT_PK_INVALID_PADDING;
      }
    
      if (block_type == LTC_LTC_PKCS_1_EME) {    /* encryption padding, we need a valid PRNG */
        if ((result = prng_is_valid(prng_idx)) != CRYPT_OK) {
           return result;
        }
      }
    
      modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
    
      /* test message size */
      if ((msglen + 11) > modulus_len) {
        return CRYPT_PK_INVALID_SIZE;
      }
    
      if (*outlen < modulus_len) {
        *outlen = modulus_len;
        result = CRYPT_BUFFER_OVERFLOW;
        goto bail;
      }
    
      /* generate an octets string PS */
      ps = &out[2];
      ps_len = modulus_len - msglen - 3;
    
      if (block_type == LTC_LTC_PKCS_1_EME) {
     #if 0
        /* now choose a random ps */
        if (prng_descriptor[prng_idx].read(ps, ps_len, prng) != ps_len) {
          result = CRYPT_ERROR_READPRNG;
          goto bail;
        }
            /* transform zero bytes (if any) to non-zero random bytes */
        for (i = 0; i < ps_len; i++) {
          while (ps[i] == 0) {
            if (prng_descriptor[prng_idx].read(&ps[i], 1, prng) != 1) {
              result = CRYPT_ERROR_READPRNG;
              goto bail;
            }
          }
        }
     #else
    	for(i = 0;i < ps_len;)
    	{
    		Security_GenerateRandData(ps + i,1);
                    if(ps[i] != 0)
                      i++;
    	}
     #endif
      } else {
        XMEMSET(ps, 0xFF, ps_len);
      }
    
      /* create string of length modulus_len */
      out[0]          = 0x00;
      out[1]          = (unsigned char)block_type;  /* block_type 1 or 2 */
      out[2 + ps_len] = 0x00;
      XMEMCPY(&out[2 + ps_len + 1], msg, msglen);
      *outlen = modulus_len;
    
      result  = CRYPT_OK;
    bail:
      return result;
    } /* pkcs_1_v1_5_encode */
    
    #endif /* #ifdef LTC_PKCS_1 */
    
    /* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_encode.c,v $ */
    /* $Revision: 1.4 $ */
    /* $Date: 2007/05/12 14:32:35 $ */

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[http_www.libtom.net]: http://www.libtom.net/
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