使用openssl api进行加密解密

[root@playmud sec]#cat sec.c
#include
#include

int do_crypt(FILE *in, FILE *out, int do_encrypt);
int main(int argc,char **argv)
{
        FILE * fin;
        FILE * fout;
        fin = fopen(argv[1], "a+");
        fout = fopen(argv[2], "a+");
        do_crypt(fin, fout, atoi(argv[3]));
        return 0;
}
int do_crypt(FILE *in, FILE *out, int do_encrypt)
{
        char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
        int inlen, outlen;
        EVP_CIPHER_CTX ctx;
        unsigned char key[] = "0123456789";
        unsigned char iv[] = "12345678";
        /* 这时候不进行key和IV的设置，因为我们还要修改参数 */
        EVP_CIPHER_CTX_init(&ctx);
        EVP_CipherInit_ex(&ctx, EVP_rc4(), NULL, NULL, NULL, do_encrypt);
        EVP_CIPHER_CTX_set_key_length(&ctx, 10);
        /* 完成参数设置，进行key和IV的设置 */
        EVP_CipherInit_ex(&ctx, NULL, NULL, key, iv, do_encrypt);

        for(;;)
          {
                inlen = fread(inbuf, 1, 1024, in);
                if(inlen <= 0) break;
                if(!EVP_CipherUpdate(&ctx, outbuf, &outlen, inbuf, inlen))
                  {
                        /*出错处理 */
                        return 0;
                  }
                fwrite(outbuf, 1, outlen, out);
          }

        if(!EVP_CipherFinal_ex(&ctx, outbuf, &outlen))
          {
                /* 出错处理*/
                return 0;
          }
        fwrite(outbuf, 1, outlen, out);
        EVP_CIPHER_CTX_cleanup(&ctx);
        return 1;
}

[root@playmud sec]# gcc -o sec sec.c -lcrypto
[root@playmud sec]# echo "abcdefg" >in.txt
[root@playmud sec]# ./sec in.txt out.txt 1
[root@playmud sec]# ls
in.txt  out.txt  sec  sec.c
[root@playmud sec]# cat out.txt
?庄~W絊[root@playmud sec]#
[root@playmud sec]# ./sec out.txt out2.txt 0
[root@playmud sec]# cat out2.txt
abcdefg