【发布时间】：2020-07-02 09:38:54
【问题描述】：
所以我正在尝试从加密例程中创建解密，但我对它的体验真的很差。谁能帮帮我吗？提前谢谢！
附言。例程写得很糟糕，故意让我们稍后更改。 编辑：对不起，这是我的整个 encry[ption 例程，我所知道的是用我的 EKey (eax) 完成的所有事情都应该保持不变，但我需要扭转用 char (ecx) 完成的事情。我真的不知道从哪里开始，再次提前谢谢。
char EKey = 'z'; //unique key:z
#define StudentName "asdasd"
#define MAXCHARS 6 // Max user input
using namespace std;
#include <string> // for strings
#include <fstream> // file I/O
#include <iostream> // for cin >> and cout <<
#include <iomanip> // for fancy output
#include "TimeUtils.h" // for GetTime, GetDate, etc.
#define dollarchar '$' // string terminator
char OChars[MAXCHARS] = { 'S','O','S','I','G',' ' }, // Original character string
EChars[MAXCHARS], // Encrypted character string
DChars[MAXCHARS] = "Soon!"; // Decrypted character string
//----------------------------- C++ Functions ----------------------------------------------------------
void get_char(char& a_character)
{
a_character = (char)_getwche();
if (a_character == '\r' || a_character == '\n') // allow the enter key to work as the terminating character too
a_character = dollarchar;
}
//-------------------------------------------------------------------------------------------------------------
void get_original_chars(int& length)
{
char next_char = ' ';
length = 0;
get_char(next_char);
while ((length < MAXCHARS) && (next_char != dollarchar))
{
OChars[length++] = next_char;
get_char(next_char);
}
}
//----------------- ENCRYPTION ROUTINES -----------------//
void encrypt_chars(int length, char EKey)
{
char temp_char; // Character temporary store
for (int i = 0; i < length; i++) // Encrypt characters one at a time
{
temp_char = OChars[i]; // Get the next char from Original Chars array
__asm
{
push eax //saves EKey to the memory stack w/ a value of 0
push ecx //saves Char to the memory stack w/ a value of 83
push edx //saves EKey to the memory stack w/ a value of 1
movzx ecx, temp_char //moves my character value (8 bit) to ecx (32 bit) w/ 0 extension which is 'S' and continues until the last character of my string.
lea eax, EKey //lea (loads effective address) puts the memory address of EKey to eax
push ecx //saves Char to the memory stack w/ a value of 83
push eax //saves Char to the memory stack w/ a value of 5241440
call encrypt_3 //calls a function in this case my unique encryption routine
add esp, 8 //adds a value of 8 to the stack pointer, esp= 5241176 + 8
mov temp_char, dl //copies the value of the encrypted Char to the current Char
pop edx //removes the encrypted char from the stack memory
pop ecx //removes the char from the stack memory
pop eax //removes the EKey from the stack memory
}
EChars[i] = temp_char; // Store encrypted char in the Encrypted Chars array
}
return;
__asm
{
encrypt_3:
push ebp //saves ebp to the stack memory
mov ebp, esp //copies the value of esp to ebp
mov eax, [ebp + 8] //adds 8 to the value of ebp then copy its value to EKey
mov ecx, [ebp + 12] //adds 12 to the value of ebp (recently added 8) then copy the value to the encrypted character
push edx //puts the edx to the stack memory
push ecx //puts CHAR to the stack memory
push eax //puts EKey to the stack memory
movzx eax, byte ptr[eax] //Uses the EKey (z) inside eax as the eax memory address
rol al, 1 //rotate al by 1 bit to the left, 111 1010 (moves the 0 at the end to the beginning)
not al //invert each bit of al (1111 0100) becomes 0000 1011
rol al, 1 //rotates the inverted binary of al to the left by 1 bit
rol al, 1 //rotates al binary by 1 bit again to the left, 0001 0110
mov edx, eax //copies the value of Ekey to edx, edx = 44
pop eax //removes the eax register from the stack memory
mov byte ptr[eax], dl //Uses the value of edx as the byte address of eax (Ekey)
pop ecx //removes the ecx (EKey) from the stack memory
xor ecx, edx //implements the XOR operation between edx and CHAR, 83 and 44 becomes 127 (111 1111)
mov eax, ecx //copy the XORed value of Char to EKey
ror al, 1 //rotates al value by 1 bit to the right 127 (0111 1111)
ror al, 1 //rotates al value by 1 bit to the right 191 (1011 1111)
ror al, 1 //rotates al value by 1 bit to the right 223 (1101 1111) al value is now 239 (1110 1111)
pop edx //removes edx from the stack memory
mov edx, eax //copy the value of EKey to edx 239 (1110 1111)
pop ebp //removes ebp from the stack memory
ret //proceeds to the line after the call instruction
}
}
//----------------- DECRYPTION ROUTINES -----------------//
void decrypt_chars(int length, char EKey)
{
char temp_char; // Character temporary store
for (int i = 0; i < length; i++) // Decrypt characters one at a time
{
temp_char = EChars[i]; // Get the next char from Encrypted Chars array
__asm
{
push eax //saves EKey to the memory stack w/ a value of 0
push ecx //saves Char to the memory stack w/ a value of 83
movzx ecx, temp_char //moves my character value (8 bit) to ecx (32 bit) w/ 0 extension which is 'S' and continues until the last character of my string.
lea eax, EKey //lea (loads effective address) puts the memory address of EKey to eax
push ecx //saves Char to the memory stack w/ a value of 83
push eax //saves Char to the memory stack w/ a value of 5241440
call decrypt_3 //calls a function in this case my unique encryption routine
add esp, 8 //adds a value of 8 to the stack pointer, esp= 5241176 + 8
mov temp_char, dl //copies the value of the encrypted Char to the current Char
pop ecx //removes the char from the stack memory
pop eax //removes the EKey from the stack memory
}
DChars[i] = temp_char; // Store decrypted char in the decrypted Chars array
}
return;
__asm
{
decrypt_3:
push ebp //saves ebp to the stack memory
mov ebp, esp //copies the value of esp to ebp
mov eax, [ebp + 8] //adds 8 to the value of ebp then copy its value to EKey
mov ecx, [ebp + 12] //adds 12 to the value of ebp (recently added 8) then copy the value to the encrypted character
push edx //puts the edx to the stack memory
push ecx //puts CHAR to the stack memory
push eax //puts EKey to the stack memory
movzx eax, byte ptr[eax] //Uses the EKey (z) inside eax as the eax memory address
rol al, 1 //rotate al by 1 bit to the left, 111 1010 (moves the 0 at the end to the beginning)
not al //invert each bit of al (1111 0100) becomes 0000 1011
rol al, 1 //rotates the inverted binary of al to the left by 1 bit
rol al, 1 //rotates al binary by 1 bit again to the left, 0001 0110
mov edx, eax //copies the value of Ekey to edx, edx = 44
pop eax //removes the eax register from the stack memory
mov byte ptr[eax], dl //Uses the value of edx as the byte address of eax (Ekey)
pop ecx //removes the ecx (EKey) from the stack memory
xor ecx, edx //implements the XOR operation between edx and CHAR, 83 and 44 becomes 127 (111 1111)
mov eax, ecx //copy the XORed value of Char to EKey
ror al, 1 //rotates al value by 1 bit to the right 127 (0111 1111)
ror al, 1 //rotates al value by 1 bit to the right 191 (1011 1111)
ror al, 1 //rotates al value by 1 bit to the right 223 (1101 1111) al value is now 239 (1110 1111)
pop edx //removes edx from the stack memory
mov edx, eax //copy the value of EKey to edx 239 (1110 1111)
pop ebp //removes ebp from the stack memory
ret //proceeds to the line after the call instruction
}
}
//----------------- end of decrypt_chars function-----------------//
//************ MAIN PROGRAM *************************************************************************************
int main(void)
{
int char_count(5); // The number of actual characters entered (upto MAXCHARS limit).
//cout << "\nPlease enter upto " << MAXCHARS << " alphanumeric characters: ";
//get_original_chars (char_count); // Input the original character string to be encrypted
//*****************************************************
// Open a file to store results (you can view and edit this file in Visual Studio)
ofstream EDump;
EDump.open("EncryptDump.txt", ios::app);
EDump << "\n\nFoCA Encryption program results (" << StudentName << ") Encryption key = '" << EKey << "'";
EDump << "\nDate: " << GetDate() << " Time: " << GetTime();
//*****************************************************
// Display and save to the EDump file the string just input
cout << "\n\nOriginal string = " << OChars << "\tHex = ";
EDump << "\n\nOriginal string = " << OChars << "\tHex = ";
for (int i = 0; i < char_count; i++)
{
cout << hex << setw(2) << setfill('0') << ((int(OChars[i])) & 0xFF) << " ";
EDump << hex << setw(2) << setfill('0') << ((int(OChars[i])) & 0xFF) << " ";
};
//*****************************************************
// Encrypt the string and display/save the result
encrypt_chars(char_count, EKey);
cout << "\n\nEncrypted string = " << EChars << "\tHex = ";
EDump << "\n\nEncrypted string = " << EChars << "\tHex = ";
for (int i = 0; i < char_count; i++)
{
cout << ((int(EChars[i])) & 0xFF) << " ";
EDump << ((int(EChars[i])) & 0xFF) << " ";
}
//*****************************************************
// Decrypt the encrypted string and display/save the result
decrypt_chars(char_count, EKey); //**** YOU NEED TO WRITE THE BODY OF THIS FUNCTION ***
cout << "\n\nDecrypted string = " << DChars << "\tHex = ";
EDump << "\n\nDecrypted string = " << DChars << "\tHex = ";
for (int i = 0; i < char_count; i++)
{
cout << ((int(DChars[i])) & 0xFF) << " ";
EDump << ((int(DChars[i])) & 0xFF) << " ";
}
//*****************************************************
cout << "\n\n\n";
EDump << "\n\n-------------------------------------------------------------";
EDump.close();
system("PAUSE");
return (0);
} // end of whole encryption/decryption program --------------------------------------------------------------------
【问题讨论】：
-
这个函数的原型是什么？一方面，它是否返回
uint64_t？这不是Minimal, Complete, Reproducible Example。 -
请说明您需要什么帮助。顺便说一句，评论您的代码将是一个非常好的主意。
-
您的编辑显示了周围的函数
encrypt_chars，但您仍然缺少main以及OChars和EChars数组的定义。请添加这些，以便尝试回答的人可以从您提供的来源运行完整的程序。此外，内联程序集似乎采用 Intel 语法。请列出您使用的编译器。 （例如，我认为gcc -m32不接受这种类型的内联汇编。这就是我可用的。）
标签： assembly x86 reverse-engineering