帮我写一份AES加密算法，不依赖系统库

对称加密算法 AES （Advanced Encryption Standard）是一种常用的加密算法，可以通过纯算法实现。以下是一个使用 VBScript 实现 AES 加密算法的示例：

' AES 加密函数
Function AESEncrypt(plainText, key)
    Dim expandedKey(), roundKeys()
    Dim state(3, 3), roundKey(3, 3)
    Dim i, j, round
    
    ' 扩展密钥
    expandedKey = KeyExpansion(key)
    
    ' 初始化状态矩阵
    For i = 0 To 3
        For j = 0 To 3
            state(i, j) = Asc(Mid(plainText, i * 4 + j + 1, 1))
        Next
    Next
    
    ' 轮密钥加
    AddRoundKey state, expandedKey, 0
    
    ' 执行 9 轮的 SubBytes、ShiftRows、MixColumns 和轮密钥加操作
    For round = 1 To 9
        SubBytes state
        ShiftRows state
        MixColumns state
        AddRoundKey state, expandedKey, round
    Next
    
    ' 执行最后一轮的 SubBytes、ShiftRows 和轮密钥加操作
    SubBytes state
    ShiftRows state
    AddRoundKey state, expandedKey, 10
    
    ' 将状态矩阵转换为字符串形式的密文
    AESEncrypt = ""
    For i = 0 To 3
        For j = 0 To 3
            AESEncrypt = AESEncrypt & Chr(state(j, i))
        Next
    Next
End Function

' 子字节替换函数
Sub SubBytes(state)
    Dim i, j
    
    For i = 0 To 3
        For j = 0 To 3
            state(j, i) = SBox(state(j, i))
        Next
    Next
End Sub

' 行移位函数
Sub ShiftRows(state)
    Dim temp(3)
    Dim i, j, k
    
    For i = 1 To 3
        For j = 0 To 3
            temp(j) = state(j, i)
        Next
        
        For j = 0 To 3
            state(j, i) = temp((j + i) Mod 4)
        Next
    Next
End Sub

' 列混淆函数
Sub MixColumns(state)
    Dim temp(3)
    Dim i, j
    
    For j = 0 To 3
        temp(0) = Mult(2, state(j, 0)) Xor Mult(3, state(j, 1)) Xor state(j, 2) Xor state(j, 3)
        temp(1) = state(j, 0) Xor Mult(2, state(j, 1)) Xor Mult(3, state(j, 2)) Xor state(j, 3)
        temp(2) = state(j, 0) Xor state(j, 1) Xor Mult(2, state(j, 2)) Xor Mult(3, state(j, 3))
        temp(3) = Mult(3, state(j, 0)) Xor state(j, 1) Xor state(j, 2) Xor Mult(2, state(j, 3))
        
        For i = 0 To 3
            state(j, i) = temp(i)
        Next
    Next
End Sub

' 轮密钥加函数
Sub AddRoundKey(state, expandedKey, round)
    Dim i, j
    
    For j = 0 To 3
        For i = 0 To 3
            state(i, j) = state(i, j) Xor expandedKey(round * 4 + i, j)
        Next
    Next
End Sub

' 密钥扩展函数
Function KeyExpansion(key)
    Dim expandedKey(44, 3)
    Dim temp(3), temp2(3)
    Dim i, j
    
    For i = 0 To 3
        For j = 0 To 3
            expandedKey(i, j) = Asc(Mid(key, i * 4 + j + 1, 1))
        Next
    Next
    
    For i = 4 To 43
        For j = 0 To 3
            temp(j) = expandedKey(i - 1, j)
        Next
        
        If i Mod 4 = 0 Then
            temp2(0) = SBox(temp(1)) Xor Rcon(i \ 4) Xor temp(0)
            temp2(1) = SBox(temp(2)) Xor 0 Xor temp(1)
            temp2(2) = SBox(temp(3)) Xor 0 Xor temp(2)
            temp2(3) = SBox(temp(0)) Xor 0 Xor temp(3)
        Else
            For j = 0 To 3
                temp2(j) = temp(j)
            Next
        End If
        
        For j = 0 To 3
            expandedKey(i, j) = expandedKey(i - 4, j) Xor temp2(j)
        Next
    Next
    
    KeyExpansion = expandedKey
End Function

' S 盒查找函数
Function SBox(byte)
    Dim row, col
    
    row = byte \ 16
    col = byte Mod 16
    
    SBox = SBoxTable(row, col)
End Function

' S 盒表
Const SBoxTable = Array( _
    &h63, &h7C, &h77, &h7B, &hF2, &h6B, &h6F, &hC5, &h30, &h01, &h67, &h2B, &hFE, &hD7, &hAB, &h76, _
    &hCA, &h82, &hC9, &h7D, &hFA, &h59, &h47, &hF0, &hAD, &hD4, &hA2, &hAF, &h9C, &hA4, &h72, &hC0, _
    &hB7, &hFD, &h93, &h26, &h36, &h3F, &hF7, &hCC, &h34, &hA5, &hE5, &hF1, &h71, &hD8, &h31, &h15, _
    &h04, &hC7, &h23, &hC3, &h18, &h96, &h05, &h9A, &h07, &h12, &h80, &hE2, &hEB, &h27, &hB2, &h75, _
    &h09, &h83, &h2C, &h1A, &h1B, &h6E, &h5A, &hA0, &h52, &h3B, &hD6, &hB3, &h29, &hE3, &h2F, &h84, _
    &h53, &hD1, &h00, &hED, &h20, &hFC, &hB1, &h5B, &h6A, &hCB, &hBE, &h39, &h4A, &h4C, &h58, &hCF, _
    &hD0, &hEF, &hAA, &hFB, &h43, &h4D, &h33, &h85, &h45, &hF9, &h02, &h7F, &h50, &h3C, &h9F, &hA8, _
    &h51, &hA3, &h40, &h8F, &h92, &h9D, &h38, &hF5, &hBC, &hB6, &hDA, &h21, &h10, &hFF, &hF3, &hD2, _
    &hCD, &h0C, &h13, &hEC, &h5F, &h97, &h44, &h17, &hC4, &hA7, &h7E, &h3D, &h64, &h5D, &h19, &h73, _
    &h60, &h81, &h4F, &hDC, &h22, &h2A, &h90, &h88, &h46, &hEE, &hB8, &h14, &hDE, &h5E, &h0B, &hDB, _
    &hE0, &h32, &h3A, &h0A, &h49, &h06, &h24, &h5C, &hC2, &hD3, &hAC, &h62, &h91, &h95, &hE4, &h79, _
    &hE7, &hC8, &h37, &h6D, &h8D, &hD5, &h4E, &hA9, &h6C, &h56, &hF4, &hEA, &h65, &h7A, &hAE, &h08, _
    &hBA, &h78, &h25, &h2E, &h1C, &hA6, &hB4, &hC6, &he8, &he3, &he1, &hef, &heb, &hed, &he6, &he0, _
    &hec, &hea, &hee, &heb, &he4, &he1, &he7, &he4 _
)

' 轮常数表
Const Rcon = Array(&h01&, &h02&, &h04&, &h08&, _
                  &h10&, &h20&, &h40&, &h80&, _
                  &h1B&, &h36&)
                  
' 有限域上的乘法运算
Function Mult(a, b)
    Dim result
    
    If a = 1 Then
        result = b
    ElseIf a = 2 Then
        result = MultBy2(b)
    ElseIf a = 3 Then
        result = MultBy3(b)
    End If
    
    Mult = result
End Function

' 有限域上乘以 2
Function MultBy2(b)
    Dim result
    
    If b < 128 Then
        result = b * 2
    Else
        result = (b * 2) Xor &h1B
    End If
    
    MultBy2 = result
End Function

' 有限域上乘以 3
Function MultBy3(b)
    Dim result
    
    result = MultBy2(b) Xor b
    
    MultBy3 = result
End Function

' 示例用法
Dim plainText, key, encryptedText

plainText = "Hello World!"
key = "MySecretKey"

encryptedText = AESEncrypt(plainText, key)
WScript.Echo "加密后的文本: " & encryptedText

请注意，这只是一个简化的 AES 加密算法实现示例，用于演示 VBScript 中的纯算法加密。在实际应用中，需要更多的安全性和可靠性考虑，建议使用专门的加密库或算法。