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舊 2006-05-05, 04:47 PM   #1
psac
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預設 MD5的算法及實現

MD5的算法及實現


MD5簡介:

MD5的全稱是Message-Digest Algorithm 5,在90年代初由MIT的電腦科學實驗室和RSA Data Security Inc發明,經MD2、MD3和MD4發展而來。

Message-Digest泛指字元串(Message)的Hash變換,就是把一個任意長度的字元串變換成一定長的大整數。請注意我使用了「字元串」而不是「字元串」這個詞,是因為這種變換只與字元的值有關,與字元集或編碼方式無關。

MD5將任意長度的「字元串」變換成一個128bit的大整數,並且它是一個不可逆的字元串變換算法,(我剛開始還愚蠢的認為MD5是可逆的算法 感謝Stkman大哥的講解)換句話說就是,即使你看到源程序和算法描述,也無法將一個MD5的值變換回原始的字元串,從數學原理上說,是因為原始的字元串有無窮多個,這有點像不存在反函數的數學函數。

MD5的典型套用是對一段Message(字元串)產生fingerprint(指紋),以防止被「篡改」。舉個例子,你將一段話寫在一個叫readme.txt文件中,並對這個readme.txt產生一個MD5的值並記錄在案,然後你可以傳播這個文件給別人,別人如果修改了文件中的任何內容,你對這個文件重新計算MD5時就會發現。如果再有一個第三方的認證機構,用MD5還可以防止文件作者的「抵賴」,這就是所謂的數位簽名套用。

MD5還廣泛用於加密和解密技術上,在很多作業系統中,用戶的密碼是以MD5值(或類似的其它算法)的方式儲存的, 用戶Login的時候,系統是把用戶輸入的密碼計算成MD5值,然後再去和系統中儲存的MD5值進行比較,而系統並不「知道」用戶的密碼是什麼。

一些黑客破獲這種密碼的方法是一種被稱為「跑字典」的方法。有兩種方法得到字典,一種是日常搜集的用做密碼的字元串表,另一種是用排列組合方法產生的,先用MD5程序計算出這些字典項的MD5值,然後再用目標的MD5值在這個字典中檢索。

即使假設密碼的最大長度為8,同時密碼只能是字母和數位,共26+26+10=62個字元,排列組合出的字典的項數則是P(62,1)+P(62,2)….+P(62,8),那也已經是一個很天文的數位了,儲存於這個字典就需要TB級的磁牒組,而且這種方法還有一個前提,就是能獲得目標賬戶的密碼MD5值的情況下才可以。

在軟體的加密保護中 很多軟體採用MD5保護 但是由於MD5算法為不可逆算法 所以所有的軟體都是使用MD5算法作為一個加密的中間步驟,比如對用戶名做一個MD5變換,結果再進去行一個可逆的加密變換,做註冊機時也只要先用MD5變換,然後再用一個逆算法。所以對於破解者來說只要能看出是MD5就很容易了。

MD5程式碼的特點明顯,跟蹤時很容易發現,如果軟體採用MD5算法,在資料啟始化的時候必然用到以下的四個常數
0x67452301;
0xefcdab89;
0x98badcfe;
0x10325476;
若常數不等 則可能是變形的MD5算法 或者根本就不是這個算法。在記憶體了也就是
01 23 45 67 89 ab cd ef fe dc ......32 10 16個字元
————————————————————————————————————————————

MD5算法:

第一步:增加填充
增加padding使得資料長度(bit為服務機構)模512為448。如果資料長度正好是模512為448,增加512個填充bit,也就是說填充的個數為1-512。第一個bit為1,其餘全部為0。
第二步:補足長度
將資料長度轉換為64bit的數值,如果長度超過64bit所能表示的資料長度的範圍,值保留最後64bit,增加到前面填充的資料後面,使得最後的資料為512bit的整數倍。也就是32bit的16倍的整數倍。在RFC1321中,32bit稱為一個word。
第三步:啟始化變數:
用到4個變數,分別為A、B、C、D,均為32bit長。啟始化為:
A: 01 23 45 67
B: 89 ab cd ef
C: fe dc ba 98
D: 76 54 32 10
第四步:資料處理:
首先定義4個輔助函數:
F(X,Y,Z) = XY v not(X) Z
G(X,Y,Z) = XZ v Y not(Z)
H(X,Y,Z) = X xor Y xor Z
I(X,Y,Z) = Y xor (X v not(Z))
其中:XY表示按位與,X v Y表示按位或,not(X)表示按位取反。xor表示按位異或。
函數中的X、Y、Z均為32bit。

定義一個需要用到的陣列:T(i),i取值1-64,T(i)等於abs(sin(i))的4294967296倍的整數部分,i為弧度。
假設前三步處理後的資料長度為32*16*Nbit

第五步:輸出:
最後得到的ABCD為輸出結果,共128bit。A為低位元,D為高位。





MD5編程實現:


下面來看看如何在C語言和VB中實現MD5算法
————————————————————————————————————————————

*/
#ifndef PROTOTYPES
#define PROTOTYPES 0
#endif
typedef unsigned char *POINTER;
typedef unsigned short int UINT2;
typedef unsigned long int UINT4;
#if PROTOTYPES
#define PROTO_LIST(list) list
#else
#define PROTO_LIST(list) ()
#endif

—————————— MD5.h————————————————————————————

typedef struct {
UINT4 state[4];
UINT4 count[2];
unsigned char buffer[64];
} MD5_CTX;

void MD5Init PROTO_LIST ((MD5_CTX *));
void MD5Update PROTO_LIST
((MD5_CTX *, unsigned char *, unsigned int));
void MD5Final PROTO_LIST ((unsigned char [16], MD5_CTX *));

※※※※※※※※※MD5C.C※※※※※※※※※※※※※※※※※※※※※※※※
#include "global.h"
#include "md5.h"
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

static void MD5Transform PROTO_LIST ((UINT4 [4], unsigned char [64]));
static void Encode PROTO_LIST
((unsigned char *, UINT4 *, unsigned int));
static void Decode PROTO_LIST
((UINT4 *, unsigned char *, unsigned int));
static void MD5_memcpy PROTO_LIST ((POINTER, POINTER, unsigned int));
static void MD5_memset PROTO_LIST ((POINTER, int, unsigned int));

static unsigned char PADDING[64] = {
0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/* 定義F G H I 為四個基數

#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
#define FF(a, b, c, d, x, s, ac) { \
(a) += F ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
(a) += G ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
(a) += H ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
(a) += I ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}

/*開始進行MD5計算
void MD5Init (context)
MD5_CTX *context;
{
context->count[0] = context->count[1] = 0;
/* 在這裡定義四個常數,也就是我們剛才講到的四個特徵數.

context->state[0] = 0x67452301;
context->state[1] = 0xefcdab89;
context->state[2] = 0x98badcfe;
context->state[3] = 0x10325476;
}

void MD5Update (context, input, inputLen)
MD5_CTX *context;
unsigned char *input;
unsigned int inputLen;
{
unsigned int i, index, partLen;

index = (unsigned int)((context->count[0] >> 3) & 0x3F);

if ((context->count[0] += ((UINT4)inputLen << 3)) < ((UINT4)inputLen << 3))
context->count[1]++;
context->count[1] += ((UINT4)inputLen >> 29);

partLen = 64 - index;

if (inputLen >= partLen) {
MD5_memcpy
((POINTER)&context->buffer[index], (POINTER)input, partLen);
MD5Transform (context->state, context->buffer);

for (i = partLen; i + 63 < inputLen; i += 64)
MD5Transform (context->state, &input);

index = 0;
}
else
i = 0;

MD5_memcpy
((POINTER)&context->buffer[index], (POINTER)&input,
inputLen-i);
}

void MD5Final (digest, context)
unsigned char digest[16];
MD5_CTX *context;
{
unsigned char bits[8];
unsigned int index, padLen;

Encode (bits, context->count, 8);

index = (unsigned int)((context->count[0] >> 3) & 0x3f);
padLen = (index < 56) ? (56 - index) : (120 - index);
MD5Update (context, PADDING, padLen);
MD5Update (context, bits, 8);

Encode (digest, context->state, 16);
MD5_memset ((POINTER)context, 0, sizeof (*context));
}

static void MD5Transform (state, block)
UINT4 state[4];
unsigned char block[64];
{
UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];

Decode (x, block, 64);

/* 第一輪循環 */
FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

/* 第二輪循環 */
GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
GG (d, a, b, c, x[10], S22, 0x2441453); /* 22 */
GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

/* 第三輪循環 */
HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
HH (b, c, d, a, x[ 6], S34, 0x4881d05); /* 44 */
HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

/* 第四輪循環 */
II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

state[0] += a;
state[1] += b;
state[2] += c;
state[3] += d;

MD5_memset ((POINTER)x, 0, sizeof (x));

}
static void Encode (output, input, len)
unsigned char *output;
UINT4 *input;
unsigned int len;
{
unsigned int i, j;

for (i = 0, j = 0; j < len; i++, j += 4) {
output[j] = (unsigned char)(input & 0xff);
output[j+1] = (unsigned char)((input >> 8) & 0xff);
output[j+2] = (unsigned char)((input >> 16) & 0xff);
output[j+3] = (unsigned char)((input >> 24) & 0xff);
}
}

static void Decode (output, input, len)
UINT4 *output;
unsigned char *input;
unsigned int len;
{
unsigned int i, j;

for (i = 0, j = 0; j < len; i++, j += 4)
output = ((UINT4)input[j]) | (((UINT4)input[j+1]) << 8) |
(((UINT4)input[j+2]) << 16) | (((UINT4)input[j+3]) << 24);
}

static void MD5_memcpy (output, input, len)
POINTER output;
POINTER input;
unsigned int len;
{
unsigned int i;

for (i = 0; i < len; i++) output = input;
}

static void MD5_memset (output, value, len)
POINTER output;
int value;
unsigned int len;
{
unsigned int i;

for (i = 0; i < len; i++)
((char *)output) = (char)value;
}
————————————————C程式碼結束——————————


在VB中實現MD5算法
——————————————————————————————————————————
Option Explicit

Dim w1 As String, w2 As String, w3 As String, w4 As String

Function MD5F(ByVal tempstr As String, ByVal w As String, ByVal X As String, ByVal y As String, ByVal z As String, ByVal Xin As String, ByVal qdata As String, ByVal rots As Integer)
MD5F = BigMod32Add(RotLeft(BigMod32Add(BigMod32Add(w, tempstr), BigMod32Add(Xin, qdata)), rots), X)
End Function

Sub MD5F1(w As String, ByVal X As String, ByVal y As String, ByVal z As String, ByVal Xin As String, ByVal qdata As String, ByVal rots As Integer)
Dim tempstr As String

tempstr = BigXOR(z, BigAND(X, BigXOR(y, z)))
w = MD5F(tempstr, w, X, y, z, Xin, qdata, rots)
End Sub

Sub MD5F2(w As String, ByVal X As String, ByVal y As String, ByVal z As String, ByVal Xin As String, ByVal qdata As String, ByVal rots As Integer)
Dim tempstr As String

tempstr = BigXOR(y, BigAND(z, BigXOR(X, y)))
w = MD5F(tempstr, w, X, y, z, Xin, qdata, rots)
End Sub

Sub MD5F3(w As String, ByVal X As String, ByVal y As String, ByVal z As String, ByVal Xin As String, ByVal qdata As String, ByVal rots As Integer)
Dim tempstr As String

tempstr = BigXOR(X, BigXOR(y, z))
w = MD5F(tempstr, w, X, y, z, Xin, qdata, rots)
End Sub

Sub MD5F4(w As String, ByVal X As String, ByVal y As String, ByVal z As String, ByVal Xin As String, ByVal qdata As String, ByVal rots As Integer)
Dim tempstr As String

tempstr = BigXOR(y, BigOR(X, BigNOT(z)))
w = MD5F(tempstr, w, X, y, z, Xin, qdata, rots)
End Sub

Function MD5_Calc(ByVal hashthis As String) As String
ReDim buf(0 To 3) As String
ReDim Xin(0 To 15) As String
Dim tempnum As Integer, tempnum2 As Integer, loopit As Integer, loopouter As Integer, loopinner As Integer
Dim a As String, b As String, c As String, d As String

tempnum = 8 * Len(hashthis)
hashthis = hashthis + Chr$(128) 'Add binary 10000000
tempnum2 = 56 - Len(hashthis) Mod 64

If tempnum2 < 0 Then
tempnum2 = 64 + tempnum2
End If

hashthis = hashthis + String$(tempnum2, Chr$(0))

For loopit = 1 To 8
hashthis = hashthis + Chr$(tempnum Mod 256)
tempnum = tempnum - tempnum Mod 256
tempnum = tempnum / 256
Next loopit


buf(0) = "67452301"
buf(1) = "efcdab89"
buf(2) = "98badcfe"
buf(3) = "10325476"


For loopouter = 0 To Len(hashthis) / 64 - 1
a = buf(0)
b = buf(1)
c = buf(2)
d = buf(3)

' Get the 512 bits
For loopit = 0 To 15
Xin(loopit) = ""
For loopinner = 1 To 4
Xin(loopit) = Hex$(Asc(Mid$(hashthis, 64 * loopouter + 4 * loopit + loopinner, 1))) + Xin(loopit)
If Len(Xin(loopit)) Mod 2 Then Xin(loopit) = "0" + Xin(loopit)
Next loopinner
Next loopit


' 第一輪循環
MD5F1 a, b, c, d, Xin(0), "d76aa478", 7
MD5F1 d, a, b, c, Xin(1), "e8c7b756", 12
MD5F1 c, d, a, b, Xin(2), "242070db", 17
MD5F1 b, c, d, a, Xin(3), "c1bdceee", 22
MD5F1 a, b, c, d, Xin(4), "f57c0faf", 7
MD5F1 d, a, b, c, Xin(5), "4787c62a", 12
MD5F1 c, d, a, b, Xin(6), "a8304613", 17
MD5F1 b, c, d, a, Xin(7), "fd469501", 22
MD5F1 a, b, c, d, Xin(8), "698098d8", 7
MD5F1 d, a, b, c, Xin(9), "8b44f7af", 12
MD5F1 c, d, a, b, Xin(10), "ffff5bb1", 17
MD5F1 b, c, d, a, Xin(11), "895cd7be", 22
MD5F1 a, b, c, d, Xin(12), "6b901122", 7
MD5F1 d, a, b, c, Xin(13), "fd987193", 12
MD5F1 c, d, a, b, Xin(14), "a679438e", 17
MD5F1 b, c, d, a, Xin(15), "49b40821", 22

' 第二輪循環
MD5F2 a, b, c, d, Xin(1), "f61e2562", 5
MD5F2 d, a, b, c, Xin(6), "c040b340", 9
MD5F2 c, d, a, b, Xin(11), "265e5a51", 14
MD5F2 b, c, d, a, Xin(0), "e9b6c7aa", 20
MD5F2 a, b, c, d, Xin(5), "d62f105d", 5
MD5F2 d, a, b, c, Xin(10), "02441453", 9
MD5F2 c, d, a, b, Xin(15), "d8a1e681", 14
MD5F2 b, c, d, a, Xin(4), "e7d3fbc8", 20
MD5F2 a, b, c, d, Xin(9), "21e1cde6", 5
MD5F2 d, a, b, c, Xin(14), "c33707d6", 9
MD5F2 c, d, a, b, Xin(3), "f4d50d87", 14
MD5F2 b, c, d, a, Xin(8), "455a14ed", 20
MD5F2 a, b, c, d, Xin(13), "a9e3e905", 5
MD5F2 d, a, b, c, Xin(2), "fcefa3f8", 9
MD5F2 c, d, a, b, Xin(7), "676f02d9", 14
MD5F2 b, c, d, a, Xin(12), "8d2a4c8a", 20

' 第三輪循環
MD5F3 a, b, c, d, Xin(5), "fffa3942", 4
MD5F3 d, a, b, c, Xin(8), "8771f681", 11
MD5F3 c, d, a, b, Xin(11), "6d9d6122", 16
MD5F3 b, c, d, a, Xin(14), "fde5380c", 23
MD5F3 a, b, c, d, Xin(1), "a4beea44", 4
MD5F3 d, a, b, c, Xin(4), "4bdecfa9", 11
MD5F3 c, d, a, b, Xin(7), "f6bb4b60", 16
MD5F3 b, c, d, a, Xin(10), "bebfbc70", 23
MD5F3 a, b, c, d, Xin(13), "289b7ec6", 4
MD5F3 d, a, b, c, Xin(0), "e27fa", 11
MD5F3 c, d, a, b, Xin(3), "d4ef3085", 16
MD5F3 b, c, d, a, Xin(6), "04881d05", 23
MD5F3 a, b, c, d, Xin(9), "d9d4d039", 4
MD5F3 d, a, b, c, Xin(12), "e6db99e5", 11
MD5F3 c, d, a, b, Xin(15), "1fa27cf8", 16
MD5F3 b, c, d, a, Xin(2), "c4ac5665", 23

' 第四輪循環
MD5F4 a, b, c, d, Xin(0), "f4292244", 6
MD5F4 d, a, b, c, Xin(7), "432aff97", 10
MD5F4 c, d, a, b, Xin(14), "ab9423a7", 15
MD5F4 b, c, d, a, Xin(5), "fc93a039", 21
MD5F4 a, b, c, d, Xin(12), "655b59c3", 6
MD5F4 d, a, b, c, Xin(3), "8f0ccc92", 10
MD5F4 c, d, a, b, Xin(10), "ffeff47d", 15
MD5F4 b, c, d, a, Xin(1), "85845dd1", 21
MD5F4 a, b, c, d, Xin(8), "6fa87e4f", 6
MD5F4 d, a, b, c, Xin(15), "fe2ce6e0", 10
MD5F4 c, d, a, b, Xin(6), "a3014314", 15
MD5F4 b, c, d, a, Xin(13), "4e0811a1", 21
MD5F4 a, b, c, d, Xin(4), "f7537e82", 6
MD5F4 d, a, b, c, Xin(11), "bd3af235", 10
MD5F4 c, d, a, b, Xin(2), "2ad7d2bb", 15
MD5F4 b, c, d, a, Xin(9), "eb86d391", 21

buf(0) = BigAdd(buf(0), a)
buf(1) = BigAdd(buf(1), b)
buf(2) = BigAdd(buf(2), c)
buf(3) = BigAdd(buf(3), d)
Next loopouter

hashthis = ""
For loopit = 0 To 3
For loopinner = 3 To 0 Step -1
hashthis = hashthis + Chr(Val("&H" + Mid$(buf(loopit), 1 + 2 * loopinner, 2)))
Next loopinner
Next loopit

MD5_Calc = hashthis
End Function

Function BigMod32Add(ByVal value1 As String, ByVal value2 As String) As String
BigMod32Add = Right$(BigAdd(value1, value2), 8)
End Function

Public Function BigAdd(ByVal value1 As String, ByVal value2 As String) As String
Dim valueans As String
Dim loopit As Integer, tempnum As Integer

tempnum = Len(value1) - Len(value2)
If tempnum < 0 Then
value1 = Space$(Abs(tempnum)) + value1
ElseIf tempnum > 0 Then
value2 = Space$(Abs(tempnum)) + value2
End If

tempnum = 0
For loopit = Len(value1) To 1 Step -1
tempnum = tempnum + Val("&H" + Mid$(value1, loopit, 1)) + Val("&H" + Mid$(value2, loopit, 1))
valueans = Hex$(tempnum Mod 16) + valueans
tempnum = Int(tempnum / 16)
Next loopit

If tempnum <> 0 Then
valueans = Hex$(tempnum) + valueans
End If

BigAdd = Right(valueans, 8)
End Function

Public Function RotLeft(ByVal value1 As String, ByVal rots As Integer) As String
Dim tempstr As String
Dim loopit As Integer, loopinner As Integer
Dim tempnum As Integer

rots = rots Mod 32

If rots = 0 Then
RotLeft = value1
Exit Function
End If

value1 = Right$(value1, 8)
tempstr = String$(8 - Len(value1), "0") + value1
value1 = ""

' 轉換成二進制形式
For loopit = 1 To 8
tempnum = Val("&H" + Mid$(tempstr, loopit, 1))
For loopinner = 3 To 0 Step -1
If tempnum And 2 ^ loopinner Then
value1 = value1 + "1"
Else
value1 = value1 + "0"
End If
Next loopinner
Next loopit
tempstr = Mid$(value1, rots + 1) + Left$(value1, rots)

' 轉換為十六進制
value1 = ""
For loopit = 0 To 7
tempnum = 0
For loopinner = 0 To 3
If Val(Mid$(tempstr, 4 * loopit + loopinner + 1, 1)) Then

tempnum = tempnum + 2 ^ (3 - loopinner)
End If
Next loopinner
value1 = value1 + Hex$(tempnum)
Next loopit

RotLeft = Right(value1, 8)
End Function

Function BigAND(ByVal value1 As String, ByVal value2 As String) As String
Dim valueans As String
Dim loopit As Integer, tempnum As Integer

tempnum = Len(value1) - Len(value2)
If tempnum < 0 Then
value2 = Mid$(value2, Abs(tempnum) + 1)
ElseIf tempnum > 0 Then
value1 = Mid$(value1, tempnum + 1)
End If

For loopit = 1 To Len(value1)
valueans = valueans + Hex$(Val("&H" + Mid$(value1, loopit, 1)) And Val("&H" + Mid$(value2, loopit, 1)))
Next loopit

BigAND = valueans
End Function

Function BigNOT(ByVal value1 As String) As String
Dim valueans As String
Dim loopit As Integer

value1 = Right$(value1, 8)
value1 = String$(8 - Len(value1), "0") + value1
For loopit = 1 To 8
valueans = valueans + Hex$(15 Xor Val("&H" + Mid$(value1, loopit, 1)))
Next loopit

BigNOT = valueans
End Function

Function BigOR(ByVal value1 As String, ByVal value2 As String) As String
Dim valueans As String
Dim loopit As Integer, tempnum As Integer

tempnum = Len(value1) - Len(value2)
If tempnum < 0 Then
valueans = Left$(value2, Abs(tempnum))
value2 = Mid$(value2, Abs(tempnum) + 1)
ElseIf tempnum > 0 Then
valueans = Left$(value1, Abs(tempnum))
value1 = Mid$(value1, tempnum + 1)
End If

For loopit = 1 To Len(value1)
valueans = valueans + Hex$(Val("&H" + Mid$(value1, loopit, 1)) Or Val("&H" + Mid$(value2, loopit, 1)))
Next loopit

BigOR = valueans
End Function

Function BigXOR(ByVal value1 As String, ByVal value2 As String) As String
Dim valueans As String
Dim loopit As Integer, tempnum As Integer

tempnum = Len(value1) - Len(value2)
If tempnum < 0 Then
valueans = Left$(value2, Abs(tempnum))
value2 = Mid$(value2, Abs(tempnum) + 1)
ElseIf tempnum > 0 Then
valueans = Left$(value1, Abs(tempnum))
value1 = Mid$(value1, tempnum + 1)
End If

For loopit = 1 To Len(value1)
valueans = valueans + Hex$(Val("&H" + Mid$(value1, loopit, 1)) Xor Val("&H" + Mid$(value2, loopit, 1)))
Next loopit

BigXOR = Right(valueans, 8)
End Function
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