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使用openssl api进行加密解密

2007-03-13 00:15 525 查看

openssl库是个好东西！

[root@playmud sec]#cat sec.c
#include <stdio.h>
#include <openssl/evp.h>

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

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