数据加密解密

如何对字符串进行加密解密

本人在操作数据库时，考虑到该数据库还有可能被其他软件打开，所以想能否有另外一种方式把数据库中数据进行加密呢，也
就是说，即使别人利用其他的软件打开了该数据库，看到的也是一片乱码，根本不知道数据库进而是什么内容。出于这种情况，本人利用VB中自带
RND（）函数的功能编写了如下加密解密方法。
当RND（）的参数（我们称它为种子）为负值时，同一种子产生同一个随机序列，同时VB还具有强大的二进制技术功能。
这样我们可以按以下方法实现字符串内容的加密解密。源程序如下：Public Function StringEnDeCodecn(strSource As String, MA) As String
'该函数只对中西文起到加密作用
'参数为：源文件，密码
On Error GoTo ErrEnDeCode
Dim X As Single
Dim CHARNUM As Long, RANDOMINTEGER As Integer
Dim SINGLECHAR As String * 1
Dim strTmp As String
If MA < 0 Then
MA = MA * (-1)
End If
X = Rnd(-MA)
For i = 1 To Len(strSource) Step 1 '取单字节内容
SINGLECHAR = Mid(strSource, i, 1)
CHARNUM = Asc(SINGLECHAR)
g: RANDOMINTEGER = Int(127 * Rnd)
If RANDOMINTEGER < 30 Or RANDOMINTEGER > 100 Then GoTo g
CHARNUM = CHARNUM Xor RANDOMINTEGER
strTmp = strTmp & Chr(CHARNUM)
Next i
StringEnDeCodecn = strTmp
Exit Function
ErrEnDeCode:
StringEnDeCodecn = ""
MsgBox Err.Number & "\" & Err.Description
End Function使用方法：
tmp=stringEnDecn("中华人民共和国",75)
如果要解密的话，只须键入以下语句：
tmp1=stringendecn(tmp,75)如有不妥之处，请与我联系：
[email protected]

64位加密方法
Option Explicit
'CIPHER.CLSPrivate mstrKey As String
Private mstrText As String'~~~.KeyString
'A string (key) used in encryption and decryption
Public Property Let KeyString(strKey As String)
    mstrKey = strKey
    Initialize
End Property'~~~.Text
'Write text to be encrypted or decrypted
Public Property Let Text(strText As String)
    mstrText = strText
End Property'Read text that was encrypted or decrypted
Public Property Get Text() As String
    Text = mstrText
End Property'~~~.DoXor
'Exclusive-or method to encrypt or decrypt
Public Sub DoXor()
On Error Resume Next
    Dim lngC As Long
    Dim intB As Long
    Dim lngN As Long
    For lngN = 1 To Len(mstrText)
        lngC = Asc(Mid(mstrText, lngN, 1))
        intB = Int(Rnd * 256)
        Mid(mstrText, lngN, 1) = Chr(lngC Xor intB)
    Next lngNEnd Sub'~~~.Stretch
'Convert any string to a printable, displayable string
Public Sub Stretch()
On Error Resume Next
    Dim lngC As Long
    Dim lngN As Long
    Dim lngJ As Long
    Dim lngK As Long
    Dim lngA As Long
    Dim strB As String
    lngA = Len(mstrText)
    strB = Space(lngA + (lngA + 2) \ 3)
    For lngN = 1 To lngA
        lngC = Asc(Mid(mstrText, lngN, 1))
        lngJ = lngJ + 1
        Mid(strB, lngJ, 1) = Chr((lngC And 63) + 59)
        Select Case lngN Mod 3
        Case 1
            lngK = lngK Or ((lngC \ 64) * 16)
        Case 2
            lngK = lngK Or ((lngC \ 64) * 4)
        Case 0
            lngK = lngK Or (lngC \ 64)
            lngJ = lngJ + 1
            Mid(strB, lngJ, 1) = Chr(lngK + 59)
            lngK = 0
        End Select
    Next lngN
    If lngA Mod 3 Then
        lngJ = lngJ + 1
        Mid(strB, lngJ, 1) = Chr(lngK + 59)
    End If
    mstrText = strB
End Sub'~~~.Shrink
'Inverse of the Stretch method;
'result can contain any of the 256-byte values
Public Sub Shrink()
On Error Resume Next
    Dim lngC As Long
    Dim lngD As Long
    Dim lngE As Long
    Dim lngA As Long
    Dim lngB As Long
    Dim lngN As Long
    Dim lngJ As Long
    Dim lngK As Long
    Dim strB As String
    lngA = Len(mstrText)
    lngB = lngA - 1 - (lngA - 1) \ 4
    strB = Space(lngB)
    For lngN = 1 To lngB
        lngJ = lngJ + 1
        lngC = Asc(Mid(mstrText, lngJ, 1)) - 59
        Select Case lngN Mod 3
        Case 1
            lngK = lngK + 4
            If lngK > lngA Then lngK = lngA
            lngE = Asc(Mid(mstrText, lngK, 1)) - 59
            lngD = ((lngE \ 16) And 3) * 64
        Case 2
            lngD = ((lngE \ 4) And 3) * 64
        Case 0
            lngD = (lngE And 3) * 64
            lngJ = lngJ + 1
        End Select
        Mid(strB, lngN, 1) = Chr(lngC Or lngD)
    Next lngN
    mstrText = strB
End Sub'Initializes random numbers using the key string
Private Sub Initialize()
    Dim lngN As Long
    Randomize Rnd(-1)
    For lngN = 1 To Len(mstrKey)
        Randomize Rnd(-Rnd * Asc(Mid(mstrKey, lngN, 1)))
    Next lngN
End Sub'-------------------------------------------------------------------------------
'Then use this code to encrypt text
Public Sub Encrypt()'call encrypt
Dim cipherTest As New Cipher 'entire encryption process
    cipherTest.KeyString = keytoencrypt.text'the key is used to encrypt the text. it can be letters and numbers
cipherTest.Text = plaintext.text'plaintext is a textbox containg what you want to encrypt
    cipherTest.DoXor
    cipherTest.Stretch
    encryptedtext.text = cipherTest.Text'encryptedtext.text is where the encrypted text will show up
End Sub
--------------------------------------------------------------------------------
'use this to decrypt
Public Sub Decrypt()'call decrypt
    Dim cipherTest As New Cipher 'entire decryption process
    cipherTest.KeyString = keyusedtodecrypt.text'keyusedtodecrypt.text is what is used to decrypt the text. It can be letters or numbers
    cipherTest.Text = textyouwantdecrypted.Text'textyouwantdecrypted is a textbox containg the text you want decrypted
    cipherTest.Shrink
    cipherTest.DoXor
    decryptedtext.Text = cipherTest.Text'decryptedtext.text is where the decrypted text will show up
    End If
End Sub
--------------------------------------------------------------------------------

字符窜最简单的加密/解密方法---异或
一次异或加密
再异或一次解密
比如字符窜A和1异或之后被加密得到字符串B
字符串B再和1异或一次又得到字符串A

调试易

数据加密解密

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