MD5介绍以及应用(c++、Qt)
什么是MD5？
MD5的全称是Message-Digest Algorithm 5，在90年代初由MIT的计算机科学实验室和RSA Data Security Inc 发明，由 MD2/MD3/MD4 发展而来的。MD5的实际应用是对一段Message(字节串)产生fingerprint(指纹)，可以防止被“篡改”。
缺点？
MD5 is no longer considered cryptographically safe for digital signatures, however, because the md5 hash function is still useful for other purposes, code is provided below.
如果不是研究加密算法，我们没必要实现自己的md5，已经有很多大神写好了：
md5.h
/* MD5
converted to C++ class by Frank Thilo ([email protected])
for bzflag (http://www.bzflag.org)
based on:
md5.h and md5.c
reference implementation of RFC 1321
Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
rights reserved.
License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.
License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.
RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.
These notices must be retained in any copies of any part of this
documentation and/or software.
*/
#ifndef BZF_MD5_H#define BZF_MD5_H
#include #include
// a small class for calculating MD5 hashes of strings or byte arrays// it is not meant to be fast or secure//// usage: 1) feed it blocks of uchars with update()// 2) finalize()// 3) get hexdigest() string// or// MD5(std::string).hexdigest()//// assumes that char is 8 bit and int is 32 bitclass MD5
{public:
typedef unsigned int size_type; // must be 32bit
MD5();
MD5(const std::string& text);
void update(const unsigned char *buf, size_type length);
void update(const char *buf, size_type length);
MD5& finalize();
std::string hexdigest() const;
friend std::ostream& operator<<(std::ostream&, MD5 md5);
private:
void init();
typedef unsigned char uint1; // 8bit
typedef unsigned int uint4; // 32bit
enum {blocksize = 64}; // VC6 won't eat a const static int here
void transform(const uint1 block[blocksize]);
static void decode(uint4 output[], const uint1 input[], size_type len);
static void encode(uint1 output[], const uint4 input[], size_type len);
bool finalized;
uint1 buffer[blocksize]; // bytes that didn't fit in last 64 byte chunk
uint4 count[2]; // 64bit counter for number of bits (lo, hi)
uint4 state[4]; // digest so far
uint1 digest[16]; // the result
// low level logic operations
static inline uint4 F(uint4 x, uint4 y, uint4 z);
static inline uint4 G(uint4 x, uint4 y, uint4 z);
static inline uint4 H(uint4 x, uint4 y, uint4 z);
static inline uint4 I(uint4 x, uint4 y, uint4 z);
static inline uint4 rotate_left(uint4 x, int n);
static inline void FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
static inline void GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
static inline void HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
static inline void II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);};
std::string md5(const std::string str);
#endifmd5.cpp
/* MD5
converted to C++ class by Frank Thilo ([email protected])
for bzflag (http://www.bzflag.org)
based on:
md5.h and md5.c
reference implemantion of RFC 1321
Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
rights reserved.
License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.
License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.
RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.
These notices must be retained in any copies of any part of this
documentation and/or software.
*/
/* interface header */#include "md5.h"
/* system implementation headers */#include 使用上面的代码：
#include #include "md5.h"
using std::cout; using std::endl;
int main(int argc, char *argv[])
{
cout << "md5 of 'grape': " << md5("grape") << endl;
return 0;
}
Qt中的MD5
qt中内置了md5算法，直接调用就可以了：
http://doc.qt.io/qt-5/qcryptographichash.html
#include <QCryptographicHash>
#include <QTextCodec>
QString function::encrypt(QString qstr)
{
QByteArray str = qstr.toAscii();
QCryptographicHash *hash = new QCryptographicHash(QCryptographicHash::Md5);
hash->addData(str);
QByteArray str1 = hash->result();
delete hash;
QTextCodec *codec = QTextCodec::codecForName("KOI8-R");
QString str_result = codec->toUnicode(str1);
return str_result;
}