C语言英文文本加密
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共2个回答
热心网友
#include "stdio.h"
#include <stdlib.h>
int main(int argc,char *argv[]){
FILE *fp,*fq;
int k,t;
fp=fopen("AAA123456701.txt","w+");
if(!fp || (fq=fopen("tmp.txt","w"))==NULL){
printf("Failed to open the file and exit...\n");
return 0;
}
printf("Please enter a short passage(letters+space+punctuation,'Enter' end)...\n");
while((t=getchar())!='\n')//为文件输入内容
fputc(t,fp);
printf("Please enter the encryption key(int >0)...\nk=");
while(scanf("%d",&k)!=1 || k<1){//输入加密密钥并判断是否正确
printf("Input error, redo: ");
fflush(stdin);
}
rewind(fp);
while(t=fgetc(fp),!feof(fp))//加密
if(t>='A' && t<='Z')
fputc(((t-'A')+k)%26+'A',fq);
else if(t>='a' && t<='z')
fputc(((t-'a')+k)%26+'a',fq);
else
fputc(t,fq);
fclose(fp);//关闭原文件
fclose(fq);//关闭加密后的文件
remove("AAA123456701.txt");//删除原文件
rename("tmp.txt","AAA123456701.txt");//将加密后的文件更换为原文件名
printf("\n");
if(fp=fopen("AAA123456701.txt","r")){
while((t=fgetc(fp))!=EOF)
printf("%c",t);
printf("\nEncryption success!\n");
}
else
printf("\nFailed to open the encrypted file...\n");
fclose(fp);
return 0;
}
代码格式和运行样例图片：
热心网友
刚好，这学期做了一个DES的加密程序。其中DES算法主体不是我写的，我只写了调用它的部分。
程序开源在Github上，你搜InformationSecurityTechnology就能搜到。
至于你的要求嘛，123点都没有直接达到，不过自己改一改不难的。主要就是第4点，实现了DES的CBC模式加密。
CBC.c：
#include "Common.c"int CBCEncrypt(Context *con)
{
InitScope();
char buffer[8]; // 因为DES_EncryptBlock允许明文和密文相同，其实也可以直接使用密文数组，但仍需memcpy一次
for (int i = 0; i < con->length; i += 8)
{
memcpy(buffer, plaintext + i, 8);
DES_XOR(buffer, prep, 8);
DES_EncryptBlock(buffer, subkeys, ciphertext + i);
prep = ciphertext + i;
}
memcpy(con->pre, prep, 8);
return 0;
}
int CBCDecrypt(Context *con)
{
InitScope();
for (int i = 0; i < con->length; i += 8)
{
DES_DecryptBlock(ciphertext + i, subkeys, plaintext + i);
DES_XOR(plaintext + i, prep, 8);
prep = ciphertext + i;
}
memcpy(con->pre, prep, 8);
return 0;
}
int main(void)
{
Run(CBCEncrypt, CBCDecrypt);
return 0;
}
Common.c：
#define _DES_c
#include "DES.c"
#endif
#include "MakeKeys.c"
#include <assert.h>
typedef struct
{
size_t length;
ElemType plainText[BUFSIZ];
ElemType cipherText[BUFSIZ];
ElemType subKeys[16][48];
ElemType pre[8];
} Context;
#define InitScope() \
assert(con->length % 8 == 0); \
ElemType *prep = con->pre; \
ElemType *plaintext = con->plainText; \
ElemType *ciphertext = con->cipherText; \
ElemType(*subkeys)[48] = con->subKeys
// void SetPre(ElemType pre[8]);
int InitContext(Context *con, const char *pw)
{
static_assert(BUFSIZ % 8 == 0, "BUFSIZ is not an integer multiple of eight");
// TODO: pw长度大于7
if (strlen(pw) > 7)
{
perror("pw too long!");
return 1;
}
char pwbuffer[7] = {0};
strncpy(pwbuffer, pw, 7);
MakeSubKeys(pwbuffer, con->subKeys);
// SetPre(con->pre);
memcpy(con->pre, "12345678", 8);
return 0;
}
int (*Encrypter)(Context *con);
int (*Decrypter)(Context *con);
#define InitIO(srcf, destf) \
FILE *srcfile = fopen((srcf), "rb"); \
FILE *destfile = fopen((destf), "wb"); \
if (srcfile == NULL || destfile == NULL) \
{ \
perror("File opening failed."); \
return 1; \
}
int DES_Encrypt(char *plainFile, char *keyStr, char *cipherFile)
{
InitIO(plainFile, cipherFile);
Context context;
InitContext(&context, keyStr);
while (0 != (context.length = fread(context.plainText, sizeof(char), BUFSIZ - 1, srcfile)))
{
// context.plainText[context.length++] = '\0';
// if (context.length % 8 != 0)
// {
// int rest = 8 - context.length % 8;
// memset(context.plainText + context.length, '\0', rest);
// context.length += rest;
// }
int rest = 8 - context.length % 8;
memset(context.plainText + context.length, '\0', rest);
context.length += rest;
assert(context.length % 8 == 0);
assert(Encrypter != NULL);
Encrypter(&context);
fwrite(context.cipherText, sizeof(ElemType), context.length, destfile);
}
fclose(srcfile);
fclose(destfile);
return 0;
}
int DES_Decrypt(char *cipherFile, char *keyStr, char *plainFile)
{
InitIO(cipherFile, plainFile);
Context context;
InitContext(&context, keyStr);
while (0 != (context.length = fread(context.cipherText, sizeof(char), BUFSIZ, srcfile)))
{
assert(context.length % 8 == 0);
assert(Decrypter != NULL);
Decrypter(&context);
// fwrite(context.plainText, sizeof(ElemType), context.length, destfile);
// fprintf(destfile, "%s", context.plainText);
fputs(context.plainText, destfile);
}
fclose(srcfile);
fclose(destfile);
return 0;
}
int Run(int (*encrypter)(Context *con), int (*decrypter)(Context *con))
{
Encrypter = (encrypter);
Decrypter = (decrypter);
char *plainfile = "plain.txt";
char *cipherfile = "cipher.bin";
char *decreptedfile = "restored.txt";
char *pw = "1234567";
DES_Encrypt(plainfile, pw, cipherfile);
DES_Decrypt(cipherfile, pw, decreptedfile);
return 0;
}
MakeKeys.c：
#ifndef _DES_c#define _DES_c
#include "DES.c"
#endif
int MakeRawKey(const char pw[7], char rawkey[56])
{
for (int i = 0; i < 7; i++)
ByteToBit(pw[i], rawkey + i * 8);
return 0;
}
int MakeKey(const char rawkey[56], ElemType key[])
{
for (int i = 0; i < 8; i++)
{
memcpy(key + 8 * i, rawkey + 7 * i, 7);
char check = 0;
for (int j = 8 * i; j < 8 * i + 7; j++)
check ^= key[j];
key[8 * i + 7] = check; // 奇数个1时check为1，即偶校验
}
return 0;
}
int MakeSubKeys(const char pw[7], ElemType subkeys[16][48])
{
char rawkey[56];
MakeRawKey(pw, rawkey);
ElemType key[];
MakeKey(rawkey, key);
DES_MakeSubKeys(key, subkeys);
return 0;
}
#define GetProperSize(x) ((x) % 8 == 0 ? (x) : ((x) + 8 - (x) % 8))
#define Length(x) (sizeof(x) / sizeof(*x))
// 不需要使用，DES_DecryptBlock中已经反向使用子密钥了
int SwapSubKeys(ElemType subkeys[16][48])
{
ElemType temp[48];
for (int i = 0; i < 8; i++)
{
memcpy(temp, subkeys[i], Length(temp));
memcpy(subkeys[i], subkeys[15 - i], 48);
memcpy(subkeys[15 - i], temp, Length(temp));
}
return 0;
}
而DES.c不是我写的，就不发了。要看去Github看。
