Question

导入Microsoft.VisualBasic

Public Class VigenereCipher

    Public Shared Function Encrypt(ByVal cipherTxt As String, ByVal key As String)
        Dim encryptedText As String = ""
        For i As Integer = 1 To cipherTxt.Length
            Dim temp As Integer = Asc(GetChar(cipherTxt, i)) _
                                  + Asc(GetChar(key, i Mod key.Length + 1))
            encryptedText += Chr(temp)
        Next
        Return encryptedText
    End Function

    Public Shared Function Decrypt(ByVal cipherTxt As String, ByVal key As String)
        Dim decryptedText As String = ""
        For i As Integer = 1 To cipherTxt.Length
            Dim temp As Integer = Asc(GetChar(cipherTxt, i)) _
                                  - Asc(GetChar(key, i Mod key.Length + 1))
            decryptedText += Chr(temp)
        Next
        Return decryptedText
    End Function

End Class

我希望程序返回常规字符，因为它会输出unicode字符。

Answer 1

直接来自MSDN：您应该使用Encoding.Convert方法

示例代码（来自MSDN）：

Public Function UnicodeToAscii( Byval unicodeString as String) As String 


  Dim ascii As Encoding = Encoding.ASCII
  Dim unicode As Encoding = Encoding.Unicode
  ' Convert the string into a byte array. 
  Dim unicodeBytes As Byte() = unicode.GetBytes(unicodeString)

  ' Perform the conversion from one encoding to the other. 
  Dim asciiBytes As Byte() = Encoding.Convert(unicode, ascii, unicodeBytes)

  ' Convert the new byte array into a char array and then into a string. 
  Dim asciiChars(ascii.GetCharCount(asciiBytes, 0, asciiBytes.Length)-1) As Char
  ascii.GetChars(asciiBytes, 0, asciiBytes.Length, asciiChars, 0)
  Dim asciiString As New String(asciiChars)
  Return asciiString
End Function

Answer 2

代码工作正常，因为我在解密后获得相同的纯文本：我使用输入Encrypt="abcdef"和key=""hxc"执行加密代码，它生成temp的输出，如下所示

何时

i=1  temp= 217 'Ù
i=2  temp= 197 'Å
i=3  temp= 203 'Ë
i=4  temp= 220 'Ò
i=5  temp= 200 'Ò
i=6  temp= 206 'Î

从进一步检查得出的结论是，对于大多数输入，您的算法将产生高于150的值。 reference表示扩展的ASCII码（字符代码128-255） 8位ASCII表有几种不同的变体。下表符合ISO 8859-1，也称为ISO Latin-1。代码129-159包含Microsoft®WindowsLatin-1扩展字符。

结论：生成Unicode字符的问题在于，您选择的算法会为127生成大于temp的值。

代码返回Unicode字符如何转换为ASCII

2 个答案: