Vigenère Cipher 维吉尼亚加解密算法

//cipher.h  额外添加的文件，用来放置相关算法，此文件独立于MFC外，可直接移植到支持CString的项目中
int* CStringToInt(CString str){
    //将CString转换为zero_based整数
    int size=str.GetLength();
    int *asc_space=new int[size];//使用new为了返回时不被消除
    for (int i=0;i<size;i++)
    {
        asc_space[i]=int(str.GetAt(i));
        if(asc_space[i]>64&&asc_space[i]<91)        //A-Z转化
            asc_space[i]-=65;
        else if(asc_space[i]>96&&asc_space[i]<123)    //a-z转化
            asc_space[i]-=97;
    }    
    return asc_space;
}

void Encode(CString key,CString plain,CString &cipher){
    //维吉尼亚加密算法
    int *keycode=CStringToInt(key);
    int *plaincode=CStringToInt(plain);
    int *ciphercode=CStringToInt(plain);
    int keysize=key.GetLength();
    int plainsize=plain.GetLength();
    int flag=0;
    CString blank(‘ ‘,plainsize+1);    //预留一个字节放\0
    cipher=blank;                    //生成空白的密文
    for (int i=0;i<plainsize;i++)
    {
        if(flag>=keysize)            //轮换钥匙
            flag=0;
        ciphercode[i]=(plaincode[i]+keycode[flag])%26;    //求密文的数字码
        cipher.SetAt(i,‘A‘+ciphercode[i]);                //生成密文
        ++flag;
    }
    cipher.SetAt(i,‘\0‘);                //在末尾放入\0
    delete keycode,plaincode,ciphercode;//释放CStringToInt()申请的空间
}

void Decode(CString key,CString &plain,CString cipher){
    //加密稍作修改就是解密算法
    int *keycode=CStringToInt(key);
    int *plaincode=CStringToInt(cipher);
    int *ciphercode=CStringToInt(cipher);
    int keysize=key.GetLength();
    int ciphersize=cipher.GetLength();
    int flag=0;
    CString blank(‘ ‘,ciphersize+1);    
    plain=blank;                    
    for (int i=0;i<ciphersize;i++)
    {
        if(flag>=keysize)    
            flag=0;
        //+26是为了对密文数字码小于密钥数字码的情况进行矫正
        plaincode[i]=(ciphercode[i]-keycode[flag]+26)%26;    
        plain.SetAt(i,‘a‘+plaincode[i]);            
        ++flag;
    }
    plain.SetAt(i,‘\0‘);
    delete keycode,plaincode,ciphercode;
}

//MFC OnButton()响应
void CVigenereCipherDlg::OnEncrypt() //加密按钮
{
    UpdateData();
    if(m_key.IsEmpty()||m_plain.IsEmpty())
        MessageBox("密钥及明文不能为空！");
    else{
        Encode(m_key,m_plain,m_cipher);//调用加密函数
        UpdateData(false);
        m_ctrEDIT1.SetReadOnly(TRUE);//防止修改密钥
        m_ctrEDIT2.SetReadOnly(TRUE);//防止修改明文
        m_ctrEDIT3.SetReadOnly(TRUE);//防止修改密文
        m_ctrEDIT4.SetReadOnly(FALSE);
    }    
}

void CVigenereCipherDlg::OnDecrypt() //解密按钮
{
    UpdateData();
    if(m_key.IsEmpty()||m_cipher.IsEmpty())
        MessageBox("密钥及密文不能为空！");
    else{
        Decode(m_key,m_explainted,m_cipher);
        UpdateData(false);
        m_explainted="";
        m_ctrEDIT1.SetReadOnly(FALSE);
        m_ctrEDIT2.SetReadOnly(FALSE);
        m_ctrEDIT3.SetReadOnly(FALSE);
        m_ctrEDIT4.SetReadOnly(TRUE);
    }
}