decrypt.cpp

aes的原代码

#include "StdAfx.h"
#include ".\decrypt.h"
/**
 * 公共构造器
 * 参数：
 *	key	密钥，从证书获得
 *	IV	初始化向量，从证书获得
 *	keyLen AES密钥长度，标准位128，192，256
 */
Decrypt::Decrypt(unsigned char *key, unsigned char *IV,int keyLen=128)
{
	this->key = new unsigned char[keyLen];
	memcpy(this->key,key,keyLen);
	//this->key = key;
	this->IV = new unsigned char[IV_LEN];
	memcpy(this->IV,IV,IV_LEN);
	//this->IV = IV;
	aes_set_key( &aesCtx, this->key, keyLen);
}
/**
 * 对缓冲区进行解密
 * 参数：
 *	debuf 源缓冲区
 *	rebuf	目标缓冲区，存放加密后的数据
 *	len 源缓冲区长度
 * 返回：加密后缓冲区有效长度 
 */
int Decrypt::DecryptBuffer(unsigned char *debuf,unsigned char *rebuf, int len)
{
	//if( (len & 0x0F ) != 0 ) throw new ::exception("buffer size not a multiple of 16!");
	if((len&0x0F)!=0) 
	{
		cout<<"buffer size not a multiple of 16!"<<endl;
		return -1;
	}
	unsigned char tmp[16];
	unsigned char buff[16];
	unsigned char *tp = rebuf;
	unsigned char *buffer = debuf;
	int offset,n,i,count=0;
	memcpy(tmpIV, IV, IV_LEN);		//备份IV
	//printf("l=%d %d\n",l,buffer[len-1]);
	for( offset = 0; offset < len; offset += 16,buffer+=16)
    {
        memcpy( buff, buffer, 16 );
		memcpy( tmp, buff, 16);
        aes_decrypt(&aesCtx, buff, buff );

        for( i = 0; i < 16; i++ )
            buff[i] ^= tmpIV[i];

        memcpy( tmpIV, tmp, 16 );
		//if(offset==0) printf("%s\n",buff);
        n = (offset == len - 16 ) ? 16-buff[15] : 16;
		if(n>16||n<0)
		{
			cout<<"填充无效！"<<endl;
			return -1;
		}
		memcpy( tp, buff, n);
		
		tp+=n;
		//count+=n;
		//printf("%d %d %d\n",n,len,buff[15]);
    }
	//printf("%d %d %d\n",n,len,buff[15]);
	count=(int)(tp-rebuf);
	//rebuf=tp;
	//memcpy(rebuf,debuf,count);
	//delete(debuf);
	return count;
}
/**
 * 静态方法，给定文件指针的位置，取得按照AES分段加密协定，解密文件时文件指针应该设置的位置
 * 参数：
 *	sectionLength 段长
 *	treamPosition 文件指针位置
 *	headerLen 文件头长度
 * 返回：解密文件时文件指针应该设置的位置（返回-1表示当前文件指针还在文件头，不能完成设置）
 */
unsigned long Decrypt::getProperPosition (int sectionLength,unsigned long streamPosition,int headerLen)
{
	long xposi = streamPosition-headerLen;
	if(xposi<0) return -1;
	return (xposi%sectionLength==0) ? streamPosition : (streamPosition-xposi%sectionLength);
}
/**
 * 根据段长和文件指针偏移计算块位置（块号）的静态方法，规定块号从0开始
 * 参数：
 *	sectionLength 段长
 *	treamPosition 文件指针位置
 *	headerLen 文件头长度
 * 返回：块号
 */
int Decrypt::getBlock(int sectionLength, unsigned long streamPosition, int headerLen)
{
	return (int)((streamPosition-headerLen)%sectionLength)/16;
}
/**
 * 根据段长和文件指针偏移计算段位置（段号）的静态方法，规定块号从0开始
 * 参数：
 *	sectionLength 段长
 *	treamPosition 文件指针位置
 *	headerLen 文件头长度
 * 返回：段号
 */
int Decrypt::getSection(int sectionLength,unsigned long streamPosition,int headerLen)
{
	return (int)((streamPosition-headerLen)/sectionLength);
}

Decrypt::~Decrypt(void)
{
	delete[] key;
	delete[] IV;
}