//CryptoAPI例程 
#ifndef _WIN32_WINNT
#define _WIN32_WINNT 0x0400
#endif

#include <stdio.h>
#include <windows.h>
#include <wincrypt.h>
#define MY_ENCODING_TYPE  (PKCS_7_ASN_ENCODING | X509_ASN_ENCODING)
#define KEYLENGTH  0x00800000

void HandleError(char *s);

//--------------------------------------------------------------------
//  These additional #define statements are required.
#define ENCRYPT_ALGORITHM CALG_RC4 
#define ENCRYPT_BLOCK_SIZE 8 

//   Declare the function EncryptFile. The function definition
//   follows main.

BOOL EncryptFile(
				 PCHAR szSource, 
				 PCHAR szDestination, 
				 PCHAR szPassword); 

//--------------------------------------------------------------------
//   Begin main.

void main(void) 
{ 
    CHAR szSource[100]; 
    CHAR szDestination[100]; 
    CHAR szPassword[100]; 
	
	
	printf("Encrypt a file. \n\n");
	printf("Enter the name of the file to be encrypted: ");
	scanf("%s",szSource);
	printf("Enter the name of the output file: ");
	scanf("%s",szDestination);
	printf("Enter the password:");
	scanf("%s",szPassword);
	
	//--------------------------------------------------------------------
	// Call EncryptFile to do the actual encryption.
	
	if(EncryptFile(szSource, szDestination, szPassword))
	{
		printf("Encryption of the file %s was a success. \n", szSource);
		printf("The encrypted data is in file %s.\n",szDestination);
	}
	else
	{
		HandleError("Error encrypting file!"); 
	} 
} // End of main

//--------------------------------------------------------------------
//   Code for the function EncryptFile called by main.

static BOOL EncryptFile(
						PCHAR szSource, 
						PCHAR szDestination, 
						PCHAR szPassword)
						//--------------------------------------------------------------------
						//   Parameters passed are:
						//     szSource, the name of the input, a plaintext file.
						//     szDestination, the name of the output, an encrypted file to be 
						//         created.
						//     szPassword, the password.
{ 
	//--------------------------------------------------------------------
	//   Declare and initialize local variables.
	
	FILE *hSource; 
	FILE *hDestination; 
	
	HCRYPTPROV hCryptProv; 
	HCRYPTKEY hKey; 
	HCRYPTHASH hHash; 
		
	PBYTE pbBuffer; 
	DWORD dwBlockLen; 
	DWORD dwBufferLen; 
	DWORD dwCount; 
	
	//--------------------------------------------------------------------
	// Open source file. 
	if(hSource = fopen(szSource,"rb"))
	{
		printf("The source plaintext file, %s, is open. \n", szSource);
	}
	else
	{ 
		HandleError("Error opening source plaintext file!");
	} 

	//--------------------------------------------------------------------
	// Open destination file. 
	if(hDestination = fopen(szDestination,"wb"))
	{
		printf("Destination file %s is open. \n", szDestination);
	}
	else
	{
		HandleError("Error opening destination ciphertext file!"); 
	}

	//以下獲得一個(gè)CSP句柄
	if(CryptAcquireContext(
		&hCryptProv, 
		NULL,				//NULL表示使用默認(rèn)密鑰容器，默認(rèn)密鑰容器名
//為用戶登陸名
		NULL, 
		PROV_RSA_FULL, 
		0))
	{
		printf("A cryptographic provider has been acquired. \n");
	}
	else
	{
		if(CryptAcquireContext(
			&hCryptProv, 
			NULL, 
			NULL, 
			PROV_RSA_FULL, 
			CRYPT_NEWKEYSET))//創(chuàng)建密鑰容器
		{
			//創(chuàng)建密鑰容器成功，并得到CSP句柄
			printf("A new key container has been created.\n");
		}
		else
		{
			HandleError("Could not create a new key container.\n");
		}
		
	}

	//--------------------------------------------------------------------
	// 創(chuàng)建一個(gè)會(huì)話密鑰（session key）
	// 會(huì)話密鑰也叫對(duì)稱密鑰，用于對(duì)稱加密算法。
	// （注: 一個(gè)Session是指從調(diào)用函數(shù)CryptAcquireContext到調(diào)用函數(shù)
	//   CryptReleaseContext 期間的階段。會(huì)話密鑰只能存在于一個(gè)會(huì)話過(guò)程）

	//--------------------------------------------------------------------
	// Create a hash object. 
	if(CryptCreateHash(
		hCryptProv, 
		CALG_MD5, 
		0, 
		0, 
		&hHash))
    {
        printf("A hash object has been created. \n");
    }
    else
    { 
		HandleError("Error during CryptCreateHash!\n");
    }  

	//--------------------------------------------------------------------
	// 用輸入的密碼產(chǎn)生一個(gè)散列
	if(CryptHashData(
		hHash, 
		(BYTE *)szPassword, 
		strlen(szPassword), 
		0))
	{
		printf("The password has been added to the hash. \n");
	}
	else
	{
		HandleError("Error during CryptHashData. \n"); 
	}

	//--------------------------------------------------------------------
	// 通過(guò)散列生成會(huì)話密鑰
	if(CryptDeriveKey(
		hCryptProv, 
		ENCRYPT_ALGORITHM, 
		hHash, 
		KEYLENGTH, 
		&hKey))
	{
		printf("An encryption key is derived from the password hash. \n"); 
	}
	else
	{
		HandleError("Error during CryptDeriveKey!\n"); 
	}
	//--------------------------------------------------------------------
	// Destroy the hash object. 
	
	CryptDestroyHash(hHash); 
	hHash = NULL; 
	
	//--------------------------------------------------------------------
	//  The session key is now ready. 
	
	//--------------------------------------------------------------------
	// 因?yàn)榧用芩惴ㄊ前碋NCRYPT_BLOCK_SIZE 大小的塊加密的，所以被加密的
// 數(shù)據(jù)長(zhǎng)度必須是ENCRYPT_BLOCK_SIZE 的整數(shù)倍。下面計(jì)算一次加密的
// 數(shù)據(jù)長(zhǎng)度。

	dwBlockLen = 1000 - 1000 % ENCRYPT_BLOCK_SIZE; 
	
	//--------------------------------------------------------------------
	// Determine the block size. If a block cipher is used, 
	// it must have room for an extra block. 
	
	if(ENCRYPT_BLOCK_SIZE > 1) 
		dwBufferLen = dwBlockLen + ENCRYPT_BLOCK_SIZE; 
	else 
		dwBufferLen = dwBlockLen; 
	
	//--------------------------------------------------------------------
	// Allocate memory. 
	if(pbBuffer = (BYTE *)malloc(dwBufferLen))
	{
		printf("Memory has been allocated for the buffer. \n");
	}
	else
	{ 
		HandleError("Out of memory. \n"); 
	}
	//--------------------------------------------------------------------
	// In a do loop, encrypt the source file and write to the source file. 
	
	do 
	{ 
		
		//--------------------------------------------------------------------
		// Read up to dwBlockLen bytes from the source file. 
		dwCount = fread(pbBuffer, 1, dwBlockLen, hSource); 
		if(ferror(hSource))
		{ 
			HandleError("Error reading plaintext!\n");
		}
		
		//--------------------------------------------------------------------
		// 加密數(shù)據(jù)
		if(!CryptEncrypt(
			hKey,			//密鑰
			0,				//如果數(shù)據(jù)同時(shí)進(jìn)行散列和加密，這里傳入一個(gè)
//散列對(duì)象
			feof(hSource),	//如果是最后一個(gè)被加密的塊，輸入TRUE.如果不是輸.
							//入FALSE這里通過(guò)判斷是否到文件尾來(lái)決定是否為
//最后一塊。
			0,				//保留
			pbBuffer,		//輸入被加密數(shù)據(jù)，輸出加密后的數(shù)據(jù)
			&dwCount,		//輸入被加密數(shù)據(jù)實(shí)際長(zhǎng)度，輸出加密后數(shù)據(jù)長(zhǎng)度
			dwBufferLen))	//pbBuffer的大小。
		{ 
			HandleError("Error during CryptEncrypt. \n"); 
		} 
		
		//--------------------------------------------------------------------
		// Write data to the destination file. 
		
		fwrite(pbBuffer, 1, dwCount, hDestination); 
		if(ferror(hDestination))
		{ 
			HandleError("Error writing ciphertext.");
		}
		
	} 
	while(!feof(hSource)); 
	//--------------------------------------------------------------------
	//  End the do loop when the last block of the source file has been
	//  read, encrypted, and written to the destination file.
	
	//--------------------------------------------------------------------
	// Close files.
	
	if(hSource) 
		fclose(hSource); 
	if(hDestination) 
		fclose(hDestination); 
	
	//--------------------------------------------------------------------
	// Free memory. 
	
	if(pbBuffer) 
		free(pbBuffer); 
	
	//--------------------------------------------------------------------
	// Destroy session key. 
	
	if(hKey) 
		CryptDestroyKey(hKey); 
	
	//--------------------------------------------------------------------
	// Destroy hash object. 
	
	if(hHash) 
		CryptDestroyHash(hHash); 
	
	//--------------------------------------------------------------------
	// Release provider handle. 
	
	if(hCryptProv) 
		CryptReleaseContext(hCryptProv, 0);
	return(TRUE); 
} // End of Encryptfile

//--------------------------------------------------------------------
//  This example uses the function HandleError, a simple error
//  handling function, to print an error message to the standard error 
//  (stderr) file and exit the program. 
//  For most applications, replace this function with one 
//  that does more extensive error reporting.

void HandleError(char *s)
{
    fprintf(stderr,"An error occurred in running the program. \n");
    fprintf(stderr,"%s\n",s);
    fprintf(stderr, "Error number %x.\n", GetLastError());
    fprintf(stderr, "Program terminating. \n");
    exit(1);
} // End of HandleError