本文目录一览：
- 1、如何用C语言对文件进行加密和解密？
- 2、C语言编程代码加密
- 3、c语言字母加密？
- 4、简单的C语言加密程序
- 5、c语言编写加密程序
如何用C语言对文件进行加密和解密？
对于加密要求不高的完全可以自己定义规则来进行加密。这种加密是很简单很自由的，例如你在存文件的时候可以将文件中的每个字符都加上一个数，然后读取该文件的时候再每个字符相应地减去那个数，即可实现就简单的加密，这样你储存的文件看上去就是乱码了。只是这个规则太简单，规则你可以自己定，加密与解密对着来就行了。
下面程序用异或操作对文件进行加密和解密
/******************设计思路******************/
//根据用户输入的加密/机密密码，
//每次都拿原文件和密码等长度的一个字符串和密码
//对应元素异或进行加密/解密
//另外因为是用异或方法，所以加密和解密就是同一个程序
//即按照同样的加密即是对文件的解密
#include
#include
#include
#include
#include
charfilename[256];//原文件
charpassword[256];//加密/解密密码
constcharfilenametemp[]="temp15435255435325432543.temp";//加密/解密中间文件
voidinputpass(char*pass);//密码输入以"******"显示
voidmain(){
FILE*fp;//加密/解密的文件
FILE*fptemp;//加密/解密过程临时文件
intpwdlen;//密码长度
inti=0;//计数器
charch=0;//读入的字符
printf("请输入要加密/解密的文件名(全路径名):\n");
gets(filename);
if((fp=fopen(filename,"rb"))==NULL){
printf("找不到文件%s\n",filename);
exit(1);
}//if
printf("请输入要加密/解密的密码:\n");
inputpass(password);
pwdlen=strlen(password);
if(pwdlen==0){
printf("密码不能为空，加密/解密失败\n");
exit(1);
}//if
fptemp=fopen(filenametemp,"wb");//打开中间文件
while(1){
ch=fgetc(fp);//从原文件读入一个字符
if(feof(fp)){//已经读到文件尾
break;//退出循环
}
ch^=password[i++];//对原字符和密码进行异或操作
fputc(ch,fptemp);//将异或结果写入中间文件
if(i==pwdlen){//使得原文件每和密码长度相同的固定长度异或加密
i=0;
}
}//while
fclose(fp);//关闭打开原文件
fclose(fptemp);//关闭打开中间文件
remove(filename);//删除原文件
rename(filenametemp,filename);//将中间文件重命名为原文件
printf("加密/解密成功\n");//至此加密/解密成功
}
//密码输入以"******"显示
voidinputpass(char*pass){
inti=0;
charc;
while(isprint(c=getch())){
pass[i++]=c;
//printf("*");
}
pass[i]='\0';
printf("\n");
}
C语言编程代码加密
例如：简单的移位加密可以这样
FILE *fp=fopen("test.txt","r");
FILE *fp1=fopen("new.txt","w");
while((c=fgetc(fp))!=EOF)
fputc(c+1,fp1);//逐个读取全部字符，ASCII值+1并保存到另一个文件
然后可以remove("test.txt");//删除文件
或者读取new.txt再写回test.txt
解密就是ASCII值-1
c语言字母加密？
按照你的要求编写的字母加密的C语言程序如下
(姓字母向后移两位,名字母向后移三位)
#includestdio.h
#includestring.h
int main(){
char src[30],result[]="",ch[2]={'\0'};
int i,j,len;
fgets(src,30,stdin);
len=strlen(src);
for(i=0;src[i]!=' ';i++){
if('a'=src[i] src[i]='z'){
ch[0]=(char)(((src[i]-'a')+2)%26+'a');
strcat(result,ch);
}else if('A'=src[i] src[i]='Z'){
ch[0]=(char)(((src[i]-'A')+2)%26+'A');
strcat(result,ch);
}else{
ch[0]=src[i];
strcat(result,ch);
}
}
for(j=i;jlen;j++){
if('a'=src[j] src[j]='z'){
ch[0]=(char)(((src[j]-'a')+3)%26+'a');
strcat(result,ch);
}else if('A'=src[j] src[j]='Z'){
ch[0]=(char)(((src[j]-'A')+3)%26+'A');
strcat(result,ch);
}else{
ch[0]=src[j];
strcat(result,ch);
}
}
printf("%s\n",result);
return 0;
}
简单的C语言加密程序
#includestdio.h
#includestdlib.h
main()
{
int key;
char ch;
printf("\n请输入密钥：");
scanf("%d",key);
printf("得到对应明文如下：");
while((ch=getchar())!='\r')
(ch+key)122?putchar(ch-122+33+key):
((ch+key)33?putchar(ch+122+key):putchar(ch+key));
}
输入输出如下：
请输入密钥：20addse
得到对应明文如下：uxx.y
你先输入一个任意的整数，如20，然后在键盘上输入一段任意的字符如addse
按回车键结束，就会得到结果 如：uxx.y
下面是另一组输入输出：
请输入密钥：35asjRYIRER!@#$^^*
得到对应明文如下：+=4u#luhuDcFG((MI-
具体是如何加密，你应该能看懂，就是用一个三目运算符 ? :控制。
c语言编写加密程序
#include stdio.h
#include string.h
#include "global.h"
#include "md5.h"
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21
static void MD5Transform PROTO_LIST ((UINT4 [4], unsigned char
[64]));
static void Encode PROTO_LIST
((unsigned char *, UINT4 *, unsigned int));
static void Decode PROTO_LIST
((UINT4 *, unsigned char *, unsigned int));
static void MD5_memcpy PROTO_LIST ((POINTER, POINTER, unsigned
int));
static void MD5_memset PROTO_LIST ((POINTER, int, unsigned int));
static unsigned char PADDING[64] = {
0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
#define F(x, y, z) (((x) (y)) | ((~x) (z)))
#define G(x, y, z) (((x) (z)) | ((y) (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))
#define ROTATE_LEFT(x, n) (((x) (n)) | ((x) (32-(n))))
#define FF(a, b, c, d, x, s, ac) { (a) += F ((b), (c), (d)) + (x) + (UINT4)(ac); (a) = ROTATE_LEFT ((a), (s)); (a) += (b);}
#define GG(a, b, c, d, x, s, ac) { \
(a) += G ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
(a) += H ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
(a) += I ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
void MD5Init (context)
MD5_CTX *context;
{
context-count[0] = context-count[1] = 0;
context-state[0] = 0x67452301;
context-state[1] = 0xefcdab89;
context-state[2] = 0x98badcfe;
context-state[3] = 0x10325476;
}
void MD5Update (context, input, inputLen)
MD5_CTX *context;
unsigned char *input;
unsigned int inputLen;
{
unsigned int i, index, partLen;
index = (unsigned int)((context-count[0] 3) 0x3F);
if ((context-count[0] += ((UINT4)inputLen 3)) ((UINT4)inputLen 3))
context-count[1]++;
context-count[1] += ((UINT4)inputLen 29);
partLen = 64 - index;
if (inputLen = partLen)
{
MD5_memcpy((POINTER)context-buffer[index], (POINTER)input, partLen);
MD5Transform (context-state, context-buffer);
for (i = partLen; i + 63 inputLen; i += 64)
MD5Transform (context-state, input[i]);
index = 0;
}
else
i = 0;
MD5_memcpy((POINTER)context-buffer[index], (POINTER)input[i],inputLen-i);
}
void MD5Final (digest, context)
unsigned char digest[16];
MD5_CTX *context;
{
unsigned char bits[8];
unsigned int index, padLen;
Encode (bits, context-count, 8);
index = (unsigned int)((context-count[0] 3) 0x3f);
padLen = (index 56) ? (56 - index) : (120 - index);
MD5Update (context, PADDING, padLen);
MD5Update (context, bits, 8);
Encode (digest, context-state, 16);
MD5_memset ((POINTER)context, 0, sizeof (*context));
}
static void MD5Transform (UINT4 state[4], unsigned char block[64])
{
UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];
Decode (x, block, 64);
FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */
/* Round 2 */
GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
GG (d, a, b, c, x[10], S22, 0x2441453); /* 22 */
GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */
/* Round 3 */
HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
HH (b, c, d, a, x[ 6], S34, 0x4881d05); /* 44 */
HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */
/* Round 4 */
II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */
state[0] += a;
state[1] += b;
state[2] += c;
state[3] += d;
MD5_memset ((POINTER)x, 0, sizeof (x));
}
static void Encode (output, input, len)
unsigned char *output;
UINT4 *input;
unsigned int len;
{
unsigned int i, j;
for (i = 0, j = 0; j len; i++, j += 4)
{
output[j] = (unsigned char)(input[i] 0xff);
output[j+1] = (unsigned char)((input[i] 8) 0xff);
output[j+2] = (unsigned char)((input[i] 16) 0xff);
output[j+3] = (unsigned char)((input[i] 24) 0xff);
}
}
static void Decode (output, input, len)
UINT4 *output;
unsigned char *input;
unsigned int len;
{
unsigned int i, j;
for (i = 0, j = 0; j len; i++, j += 4)
output[i] = ((UINT4)input[j]) | (((UINT4)input[j+1]) 8) |(((UINT4)input[j+2]) 16) | (((UINT4)input[j+3]) 24);
}
static void MD5_memcpy (output, input, len)
POINTER output;
POINTER input;
unsigned int len;
{
unsigned int i;
for (i = 0; i len; i++)
output[i] = input[i];
}
static void MD5_memset (output, value, len)
POINTER output;
int value;
unsigned int len;
{
unsigned int i;
for (i = 0; i len; i++)
((char *)output)[i] = (char)value;
}
#ifndef MD
#define MD 5
#endif
#define TEST_BLOCK_LEN 1000
#define TEST_BLOCK_COUNT 1000
static void MDString PROTO_LIST ((char *));
static void MDPrint PROTO_LIST ((unsigned char [16]));
#define MD_CTX MD5_CTX
#define MDInit MD5Init
#define MDUpdate MD5Update
#define MDFinal MD5Final
int main (int argc, char *argv[])
{
int i;
if (argc 1)
{ MDString(argv[1]);
return (0);
}
}
static void MDString (char *string)
{
MD_CTX context;
unsigned char digest[16];
unsigned int len = strlen (string);
MDInit (context);
MDUpdate (context, string, len);
MDFinal (digest, context);
printf ("MD%d (\"%s\") = ", MD, string);
MDPrint (digest);
printf ("\n");
}
static void MDPrint (unsigned char digest[16])
{
unsigned int i;
for (i = 0; i 16; i++)
printf ("%02x", digest[i]);
}
