问一个关于base64加密的有关问题
问一个关于base64加密的问题
网上看到一位牛人写的一个base64的加密程序：
他把tmp[0]和tmp[2]对调之后顺序变成了tmp[2],tmp[1],tmp[0],是不是强制转换成struct Base64Date6 *的时候是从tmp[0]开始转换，最后转换到tmp[2]的？
小弟是业余的，对堆栈什么的只懂一丁点，希望各位大神能够赐教！
------解决思路----------------------
temp是一个三字节的数组，刚好是3*8=24bit.Base64Date6结构体是4*6=24bit.二者的长度是一样的。
那个交换是将第三字节和第一字节交换，然后按照Base64Date6结构的方式来访问操作
------解决思路----------------------
仅供参考
网上看到一位牛人写的一个base64的加密程序：
struct Base64Date6
{
unsigned int d4:6;
unsigned int d3:6;
unsigned int d2:6;
unsigned int d1:6;
};
char ConvertToBase64(char uc)
{
if(uc < 26)
{
return 'A' + uc;
}
if(uc < 52)
{
return 'a' + (uc - 26);
}
if(uc < 62)
{
return '0' + (uc - 52);
}
if(uc == 62)
{
return '+';
}
return '/';
}
// base64的实现
void EncodeBase64(char *dbuf, char *buf128, int len)///
{
struct Base64Date6 *ddd = NULL;
int i = 0;
char buf[256] = {0};
char *tmp = NULL;
char cc = '\0';
memset(buf, 0, 256);///
strcpy(buf, buf128);///
for(i = 1; i <= len/3; i++)
{
tmp = buf + (i-1)*3;
cc = tmp[2];
tmp[2] = tmp[0];
tmp[0] = cc;
ddd = (struct Base64Date6 *)tmp;///强制转换这一步
dbuf[(i-1)*4+0] = ConvertToBase64((unsigned int)ddd->d1);
dbuf[(i-1)*4+1] = ConvertToBase64((unsigned int)ddd->d2);
dbuf[(i-1)*4+2] = ConvertToBase64((unsigned int)ddd->d3);
dbuf[(i-1)*4+3] = ConvertToBase64((unsigned int)ddd->d4);
}
if(len % 3 == 1)
{
tmp = buf + (i-1)*3;
cc = tmp[2];
tmp[2] = tmp[0];
tmp[0] = cc;
ddd = (struct Base64Date6 *)tmp;
dbuf[(i-1)*4+0] = ConvertToBase64((unsigned int)ddd->d1);
dbuf[(i-1)*4+1] = ConvertToBase64((unsigned int)ddd->d2);
dbuf[(i-1)*4+2] = '=';
dbuf[(i-1)*4+3] = '=';
}
if(len%3 == 2)
{
tmp = buf+(i-1)*3;
cc = tmp[2];
tmp[2] = tmp[0];
tmp[0] = cc;
ddd = (struct Base64Date6 *)tmp;
dbuf[(i-1)*4+0] = ConvertToBase64((unsigned int)ddd->d1);
dbuf[(i-1)*4+1] = ConvertToBase64((unsigned int)ddd->d2);
dbuf[(i-1)*4+2] = ConvertToBase64((unsigned int)ddd->d3);
dbuf[(i-1)*4+3] = '=';
}
return;
}
他把tmp[0]和tmp[2]对调之后顺序变成了tmp[2],tmp[1],tmp[0],是不是强制转换成struct Base64Date6 *的时候是从tmp[0]开始转换，最后转换到tmp[2]的？
小弟是业余的，对堆栈什么的只懂一丁点，希望各位大神能够赐教！
------解决思路----------------------
temp是一个三字节的数组，刚好是3*8=24bit.Base64Date6结构体是4*6=24bit.二者的长度是一样的。
那个交换是将第三字节和第一字节交换，然后按照Base64Date6结构的方式来访问操作
------解决思路----------------------
仅供参考
#pragma comment(lib,"crypt32")
#include <windows.h>
#include <stdio.h>
#include <tchar.h>
//+-------------------------------------------------------------------------
// convert formatted string to binary
// If cchString is 0, then pszString is NULL terminated and
// cchString is obtained via strlen() + 1.
// dwFlags defines string format
// if pbBinary is NULL, *pcbBinary returns the size of required memory
// *pdwSkip returns the character count of skipped strings, optional
// *pdwFlags returns the actual format used in the conversion, optional
//--------------------------------------------------------------------------
BOOL
WINAPI
CryptStringToBinaryA(
IN LPCSTR pszString,
IN DWORD cchString,
IN DWORD dwFlags,
IN BYTE *pbBinary,
IN OUT DWORD *pcbBinary,
OUT DWORD *pdwSkip, //OPTIONAL
OUT DWORD *pdwFlags //OPTIONAL
);
//+-------------------------------------------------------------------------
// convert formatted string to binary
// If cchString is 0, then pszString is NULL terminated and
// cchString is obtained via strlen() + 1.
// dwFlags defines string format
// if pbBinary is NULL, *pcbBinary returns the size of required memory
// *pdwSkip returns the character count of skipped strings, optional
// *pdwFlags returns the actual format used in the conversion, optional
//--------------------------------------------------------------------------
BOOL
WINAPI
CryptStringToBinaryW(
IN LPCWSTR pszString,
IN DWORD cchString,
IN DWORD dwFlags,
IN BYTE *pbBinary,
IN OUT DWORD *pcbBinary,
OUT DWORD *pdwSkip, //OPTIONAL
OUT DWORD *pdwFlags //OPTIONAL
);
#ifdef UNICODE
#define CryptStringToBinary CryptStringToBinaryW
#else
#define CryptStringToBinary CryptStringToBinaryA
#endif // !UNICODE
//+-------------------------------------------------------------------------
// convert binary to formatted string
// dwFlags defines string format
// if pszString is NULL, *pcchString returns the size of required memory in byte
//--------------------------------------------------------------------------
BOOL
WINAPI
CryptBinaryToStringA(
IN CONST BYTE *pbBinary,
IN DWORD cbBinary,
IN DWORD dwFlags,
IN LPSTR pszString,
IN OUT DWORD *pcchString
);
//+-------------------------------------------------------------------------
// convert binary to formatted string
// dwFlags defines string format
// if pszString is NULL, *pcchString returns the size of required memory in byte
//--------------------------------------------------------------------------
BOOL
WINAPI
CryptBinaryToStringW(
IN CONST BYTE *pbBinary,
IN DWORD cbBinary,
IN DWORD dwFlags,
IN LPWSTR pszString,
IN OUT DWORD *pcchString
);
#ifdef UNICODE
#define CryptBinaryToString CryptBinaryToStringW
#else
#define CryptBinaryToString CryptBinaryToStringA
#endif // !UNICODE
// dwFlags has the following defines
#define CRYPT_STRING_BASE64HEADER 0x00000000
#define CRYPT_STRING_BASE64 0x00000001
#define CRYPT_STRING_BINARY 0x00000002
#define CRYPT_STRING_BASE64REQUESTHEADER 0x00000003
#define CRYPT_STRING_HEX 0x00000004
#define CRYPT_STRING_HEXASCII 0x00000005
#define CRYPT_STRING_BASE64_ANY 0x00000006
#define CRYPT_STRING_ANY 0x00000007
#define CRYPT_STRING_HEX_ANY 0x00000008
#define CRYPT_STRING_BASE64X509CRLHEADER 0x00000009
#define CRYPT_STRING_HEXADDR 0x0000000a
#define CRYPT_STRING_HEXASCIIADDR 0x0000000b
#define CRYPT_STRING_NOCR 0x80000000
// CryptBinaryToString uses the following flags
// CRYPT_STRING_BASE64HEADER - base64 format with certificate begin
// and end headers
// CRYPT_STRING_BASE64 - only base64 without headers
// CRYPT_STRING_BINARY - pure binary copy
// CRYPT_STRING_BASE64REQUESTHEADER - base64 format with request begin
// and end headers
// CRYPT_STRING_BASE64X509CRLHEADER - base64 format with x509 crl begin
// and end headers
// CRYPT_STRING_HEX - only hex format
// CRYPT_STRING_HEXASCII - hex format with ascii char display
// CRYPT_STRING_HEXADDR - hex format with address display
// CRYPT_STRING_HEXASCIIADDR - hex format with ascii char and address display
//
// CryptBinaryToString accepts CRYPT_STRING_NOCR or'd into one of the above.
// When set, line breaks contain only LF, instead of CR-LF pairs.
// CryptStringToBinary uses the following flags
// CRYPT_STRING_BASE64_ANY tries the following, in order:
// CRYPT_STRING_BASE64HEADER
// CRYPT_STRING_BASE64
// CRYPT_STRING_ANY tries the following, in order:
// CRYPT_STRING_BASE64_ANY
// CRYPT_STRING_BINARY -- should always succeed
// CRYPT_STRING_HEX_ANY tries the following, in order:
// CRYPT_STRING_HEXADDR
// CRYPT_STRING_HEXASCIIADDR
// CRYPT_STRING_HEXASCII
// CRYPT_STRING_HEX
char *flags[12]={
"CRYPT_STRING_BASE64HEADER",
"CRYPT_STRING_BASE64",
"CRYPT_STRING_BINARY",
"CRYPT_STRING_BASE64REQUESTHEADER",
"CRYPT_STRING_HEX",
"CRYPT_STRING_HEXASCII",
"CRYPT_STRING_BASE64_ANY",
"CRYPT_STRING_ANY",
"CRYPT_STRING_HEX_ANY",
"CRYPT_STRING_BASE64X509CRLHEADER",
"CRYPT_STRING_HEXADDR",
"CRYPT_STRING_HEXASCIIADDR",
};
#define MAXC 1024
BYTE b[22]={
0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E,0x0F,
0x41,0x42,0xB0,0xA1,0x4A,0x55,
};
BOOL r;
DWORD len,dwFlags;
TCHAR s[MAXC];
int _tmain() {
_tprintf(_T("API CryptBinaryToString in crypt32.dll Demonstration:\n"));
for (dwFlags=0;dwFlags<12;dwFlags++) {
if (dwFlags==2
------解决思路----------------------
dwFlags==6
------解决思路----------------------
dwFlags==7
------解决思路----------------------
dwFlags==8) continue;
r=CryptBinaryToString(b,22,dwFlags,NULL,&len);
if (!r) {
_tprintf(_T("CryptBinaryToString error!\n"));
return 1;
}
if (len>MAXC) {
_tprintf(_T("%d==len>MAXC==%d!\n"),len,MAXC);
return 2;
}
r=CryptBinaryToString(b,22,dwFlags,s,&len);
if (!r) {
_tprintf(_T("CryptBinaryToString error!\n"));
return 3;
}
_tprintf(_T("\n%s:[\n%s]\n"),flags[dwFlags],s);
}
return 0;
}
//API CryptBinaryToString in crypt32.dll Demonstration:
//
//CRYPT_STRING_BASE64HEADER:[
//-----BEGIN CERTIFICATE-----
//AAECAwQFBgcICQoLDA0OD0FCsKFKVQ==
//-----END CERTIFICATE-----
//]
//
//CRYPT_STRING_BASE64:[
//AAECAwQFBgcICQoLDA0OD0FCsKFKVQ==
//]
//
//CRYPT_STRING_BASE64REQUESTHEADER:[
//-----BEGIN NEW CERTIFICATE REQUEST-----
//AAECAwQFBgcICQoLDA0OD0FCsKFKVQ==
//-----END NEW CERTIFICATE REQUEST-----
//]
//
//CRYPT_STRING_HEX:[
// 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
// 41 42 b0 a1 4a 55
//]
//
//CRYPT_STRING_HEXASCII:[
// 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f ................
// 41 42 b0 a1 4a 55 AB..JU
//]
//
//CRYPT_STRING_BASE64X509CRLHEADER:[
//-----BEGIN X509 CRL-----
//AAECAwQFBgcICQoLDA0OD0FCsKFKVQ==
//-----END X509 CRL-----
//]
//
//CRYPT_STRING_HEXADDR:[
//0000 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
//0010 41 42 b0 a1 4a 55
//]
//
//CRYPT_STRING_HEXASCIIADDR:[
//0000 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f ................
//0010 41 42 b0 a1 4a 55 AB..JU
//]
//