c# - C# 和经典 ASP 之间的 Blowfish 结果不同

Question

我需要在 C# 中加密一个值，然后在经典 ASP 中解密它。我最接近使它起作用的是 Blowfish。但问题是这两种实现产生的结果略有不同，我不确定为什么。

正在使用的实现:

C#:https://defuse.ca/blowfish.htm

vbscript: http://www.di-mgt.com.au/cryptoBlowfishASP.html

C#代码:

var input = "Hello World";
var key = "04B915BA43FEB5B6";
BlowFish b = new BlowFish(key);

string enc, dec;

enc = b.Encrypt_ECB(input);
dec = b.Decrypt_ECB(enc);

脚本:

Dim aKey()
Dim nKeyLen, szTxtKey, szTxtPlain, szTxtKeyAsString, szTxtCipher, szTxtCipherHex, szTxtCipher64, szTxtDecrypt

szTxtKey = "04B915BA43FEB5B6"
szTxtPlain = "Hello World"

ReDim aKey((Len(szTxtKey) \ 2) - 1)
nKeyLen = bu_HexStr2Bytes(szTxtKey, aKey)
Call blf_Key(aKey, nKeyLen)
szTxtKeyAsString = bu_Bytes2HexStr(aKey, nKeyLen) 

szTxtCipher = blf_StringEnc(szTxtPlain)
szTxtCipherHex = bu_Str2Hex(szTxtCipher) 

C# 输出:

819dd50a925a5eb83ed723bea6d84984

VBScript 输出:

819DD50A925A5EB8CABE974A654A18A8

前半部分输出相同:“819DD50A925A5EB8”

有趣的是，如果我用 C# 库解密 vbscript 输出，我会得到: Hello World ♣♣♣♣♣

所以...它几乎可以工作，但是有某种填充或其他事情正在发生。不过我不知道如何解决这个问题。

Answer 1

作为@artjom-b有already mentioned in the comments ，罪魁祸首是不同的填充。

对不同的填充方法有很好的解释here .

分析 blowfish.cs 文件显示它使用 NULL 填充(注意文件中的这个片段)；

/// <summary>
/// Decrypts a string (ECB)
/// </summary>
/// <param name="ct">hHex string of the ciphertext</param>
/// <returns>Plaintext ascii string</returns>
public string Decrypt_ECB(string ct)
{
    return Encoding.ASCII.GetString(Decrypt_ECB(HexToByte(ct))).Replace("\0", "");
}

相比之下，经典 ASP 实现使用 PKCS5 填充(来自 basBlowfishFns.asp 的片段显示了 PKCS5 方法)

^{From Using Padding in Encryption}
Pad with bytes all of the same value as the number of padding bytes (PKCS5 padding)

' Get # of padding bytes from last char
nPad = Asc(Right(strData, 1))
If nPad > 8 Then nPad = 0   ' In case invalid
strData = Left(strData, nLen - nPad)

解决方法是对 c# 库使用的 NULL 填充应用变通方法。

这是修改后的basBlowfishFns.asp (仅显示修改后的功能)；

Public Function blf_StringEnc(strData, padMethod)
' Encrypts plaintext strData after adding RFC 2630 padding
' Returns encrypted string.
' Requires key and boxes to be already set up.
' Version 5. Completely revised.
' The speed improvement here is due to Robert Garofalo.
    Dim strIn
    Dim strOut
    Dim nLen
    Dim sPad
    Dim nPad
    Dim nBlocks
    Dim i
    Dim j
    Dim aBytes(7)
    Dim sBlock
    Dim iIndex

    ' Pad data string to multiple of 8 bytes
    strIn = PadString(strData, padMethod)
    ' Calc number of 8-byte blocks
    nLen = Len(strIn)
    nBlocks = nLen \ 8
    ' Allocate output string here so we can use Mid($ below
    ' strOut = String(nLen, " ")
    strOut = ""     ' Fix for VBScript

    ' Work through string in blocks of 8 bytes
    iIndex = 0
    For i = 1 To nBlocks
        sBlock = Mid(strIn, iIndex + 1, 8)
        ' Convert to bytes
        ' aBytes() = StrConv(sBlock, vbFromUnicode)
        Call bu_String2Bytes(sBlock, aBytes)
        ' Encrypt the block
        Call blf_EncryptBytes(aBytes)
        ' Convert back to a string
        ' sBlock = StrConv(aBytes(), vbUnicode)
        sBlock = bu_Bytes2String(aBytes, 8)
        ' Copy to output string
        ' Mid(strOut, iIndex + 1, 8) = sBlock
        strOut = strOut & sBlock
        iIndex = iIndex + 8
    Next

    blf_StringEnc = strOut

End Function

Public Function blf_StringDec(strData, padMethod)
' Decrypts ciphertext strData and removes RFC 2630 padding
' Returns decrypted string.
' Requires key and boxes to be already set up.
' Version 5. Completely revised.
' The speed improvement here is due to Robert Garofalo.
    Dim strIn
    Dim strOut
    Dim nLen
    Dim sPad
    Dim nPad
    Dim nBlocks
    Dim i
    Dim j
    Dim aBytes(7)
    Dim sBlock
    Dim iIndex

    strIn = strData
    ' Calc number of 8-byte blocks
    nLen = Len(strIn)
    nBlocks = nLen \ 8
    ' Allocate output string here so we can use Mid($ below
    'strOut = String(nLen, " ")
    strOut = ""

    ' Work through string in blocks of 8 bytes
    iIndex = 0
    For i = 1 To nBlocks
        sBlock = Mid(strIn, iIndex + 1, 8)
        ' Convert to bytes
        ' aBytes() = StrConv(sBlock, vbFromUnicode)
        Call bu_String2Bytes(sBlock, aBytes)
        ' Encrypt the block
        Call blf_DecryptBytes(aBytes)
        ' Convert back to a string
        'sBlock = StrConv(aBytes(), vbUnicode)
        sBlock = bu_Bytes2String(aBytes, 8)
        ' Copy to output string
        ' Mid(strOut, iIndex + 1, 8) = sBlock
        strOut = strOut & sBlock
        iIndex = iIndex + 8
    Next

    ' Strip padding, if valid
    strOut = UnpadString(strOut, padMethod)

    blf_StringDec = strOut

End Function

Public Function PadString(strData, method)
' Pad data string to next multiple of 8 bytes as per RFC 2630
    Dim nLen
    Dim sPad
    Dim nPad
    nLen = Len(strData)
    nPad = ((nLen \ 8) + 1) * 8 - nLen
    Select Case method
    Case "PKCS5"
        sPad = String(nPad, Chr(nPad))  ' Pad with # of pads (1-8)
    Case "NULL"
        sPad = String(nPad, Chr(0))  ' Pad with # of NULL characters
    End Select
    PadString = strData & sPad

End Function

Public Function UnpadString(strData, method)
' Strip RFC 2630-style padding
    Dim nLen
    Dim nPad
    nLen = Len(strData)
    If nLen = 0 Then Exit Function
    Select Case method
    Case "PKCS5"
        ' Get # of padding bytes from last char
        nPad = Asc(Right(strData, 1))
        If nPad > 8 Then nPad = 0   ' In case invalid
        strData = Left(strData, nLen - nPad)
    Case "NULL"
        'Remove any NULL characters, obviously, this method isn't ideal if
        'the data contains valid NULLs. This shouldn't be an issue with
        'ASCII text.
        strData = Replace(strData, Chr(0), "")
    End Select
    UnpadString = strData
End Function

主要修改是 PadString() 和 UnpadString() 函数。我添加了一个参数 method 允许您传递标识符 NULL 或 PKCS5 以确定我们如何填充/取消填充数据。这些函数已经存在，但出于某种原因未被 blf_StringEnc() 和 blf_StringDec() 函数使用，因此符合 DRY principle 的利益。我修改了它们以便使用它们。

通过这些修改(这只是使代码更灵活的快速尝试) 使用以下代码；

Dim aKey()
Dim nKeyLen, szTxtKey, szTxtPlain, szTxtKeyAsString, szTxtCipher, szTxtCipherHex, szTxtCipher64, szTxtDecrypt

szTxtKey = "04B915BA43FEB5B6"
szTxtPlain = "Hello World"

ReDim aKey((Len(szTxtKey) \ 2) - 1)
nKeyLen = bu_HexStr2Bytes(szTxtKey, aKey)
Call blf_Key(aKey, nKeyLen)
szTxtKeyAsString = bu_Bytes2HexStr(aKey, nKeyLen) 

'Encrypt using NULL padding method.
szTxtCipher = blf_StringEnc(szTxtPlain, "NULL")
szTxtCipherHex = bu_Str2Hex(szTxtCipher)

Call Response.Write(szTxtCipherHex)

将导致；

819DD50A925A5EB83ED723BEA6D84984

正如最初预期的那样。