Principles and system development of truecrypt (1): Create an encrypted volume using truecrypt format

 

 

I. Overview
Truecrypt is the only virtual encrypted disk software that supports Windows Vista/XP/2000/Linux open source. It can create and set encrypted virtual disk images, and the virtual disk can be accessed as normal as other disks, all internal files are automatically encrypted and accessed using passwords. encryption and decryption are both real-time.
Truecrypt consists of two parts: truecrypt format, which is used to create an encrypted volume and truecrypt mount, which is used to load and detach a virtual disk to a partition.

Part 1: Create an encrypted volume using truecrypt format
The wizard for creating an encrypted volume according to the truecrypt format shows the location, algorithm, size, password, and format of the encrypted volume, then the encrypted volume is created. The created encrypted volume is the file at which the encrypted volume is located.

Therefore, we know that the core of truecrypt is to create an encrypted volume function. This function is used to accept the preceding parameters such as the location of the encrypted volume to complete the creation process, the prototype in truecrypt is

 

Int formatvolume (char * volumepath, <br/> bool bdevice, <br/> unsigned _ int64 size, <br/> unsigned _ int64 hiddenvolhostsize, <br/> password * password, <br/> int cipher, <br/> int pkcs5, <br/> bool quickformat, <br/> bool sparsefileswitch, <br/> int filesystem, <br/> int clustersize, <br/> hwnd hwnddlg, <br/> bool hiddenvol, <br/> int * realclustersize, <br/> bool UAC ); 

Next, let's take a look at the specific meaning of each parameter.

 

Parameters	Type	Description	Example
Volumepath	Char *	Encrypted volume file selected	C: // 1.txt
Bdevice	Bool	Whether it is a partition volume	False
Size	Unsigned _ int64	Size of the encrypted volume (in bytes)	10*1024*1024
Hiddenvolhostsize	Unsigned _ int64	Hide the size of the encrypted volume (in bytes)	0
Password	Password	Password entered by the user	123456
Cipher	Int	Default encryption algorithm	1
Pkcs5	Int	Hash Algorithm	Default_hash_algorithm
Quickformat	Bool	Is it quick format?	False
Sparsefileswitch	Bool		True
Filesystem	Int	File System	Filesys_fat
Clustersize	Int		0
Hwnddlg	Hwnd	Input window handle	Null
Hiddenvol	Bool	Whether the volume is hidden	False
Realclustersize	Int		512
UAC	Bool		False

 

Next let's look at the specific example

 

Int format (char * szfile, unsigned _ int64 nsize, char * szpassword, hwnd hwnddlg) <br/>{< br/> char szfilename [tc_max_path + 1]; /* the file selected by the user */<br/> char szdiskfile [tc_max_path + 1]; /* fully qualified name derived from szfilename */<br/> bool bdevice = false;/* Is this a partition volume? */<Br/> unsigned _ int64 nvolumesize = 0;/* The volume size, in bytes. */<br/> unsigned _ int64 nhiddenvolhostsize = 0;/* size of the hidden volume host, in bytes */<br/> password volumepassword; /* users password */<br/> int nvolumeea = 1;/* default encryption algorithm */<br/> int hash_algo = default_hash_algorithm; /* which PRF to use in Header key derivation (PKCS #5) and in the RNG. */<br/> volatile bool bsparsefileswitch = false; <br/> volatile bool quickformat = false;/* warning: meaning of this variable depends on bsparsefileswitch. */<br/>/* If bsparsefileswitch is true, this variable represents the sparse file flag. */<br/> volatile int filesystem = 0; <br/> volatile int clustersize = 0; <br/> bool bhidden; <br/> int realclustersize; /* parameter used when determining the maximum possible size of a hidden volume. */<br/> int nstatus; <br/> char sztmp [16]; <br/> int nmultiplier = 1024*1024;/* Size Selection multiplier. */<br/> // strcpy (szdiskfile, "C: // 1.txt"); <br/> // szdiskfile [8] = 0; <br/> strcpy (szdiskfile, szfile); <br/> szdiskfile [strlen (szfile)] = 0; <br/> strcpy (sztmp, "10 "); <br/> // nvolumesize = _ atoi64 (sztmp); <br/> nvolumesize = nsize; <br/> nvolumesize = nvolumesize * nmultiplier; <br/> nhiddenvolhostsize = 0; <br/> // strcpy (volumepassword. text, "123456"); <br/> strcpy (volumepassword. text, szpassword); <br/> volumepassword. length = strlen (volumepassword. text); <br/> quickformat = false; <br/> bsparsefileswitch = true; <br/> filesystem = filesys_fat; <br/> clustersize = 0; <br/> bhidden = false; <br/> realclustersize = 512; </P> <p> nstatus = formatvolume (szdiskfile, // <br/> bdevice, // <br/> nvolumesize, // 1024*1024*10 <br/> nhiddenvolhostsize, // 0 <br/> & volumepassword, // <br/> nvolumeea, // <br/> hash_algo, // <br/> quickformat, // false <br/> bsparsefileswitch, // true <br/> filesystem, // 1 <br/> clustersize, // 0 <br/> hwnddlg, // <br/> bhidden, // false <br/> & realclustersize, /// 512 <br/> false); <br/> return 1; <br/>} 

 

After setting a series of parameters, you can complete the setting of the encrypted volume. Now you can create an encrypted volume. You can use the preceding method to create the encrypted volume. Truecrypt has no limit on the size of the encrypted volume file. The size of the virtual disk is limited only by the file system of the disk where the encrypted volume is located. For example, the encrypted volume file that can be created in a disk that is FAT32 formatted cannot exceed 4 GB.