VB.NET Rijndael管理加密或AES有多安全？

Question

我正在使用此代码的略微修改版本.创建关键任务应用程序.那些将被加密的文件非常重要.这必须从头开始,因为还有一些其他事情需要与此一起完成.

这有多安全？它不可能破解这种加密吗？

很抱歉,这是一个有用的链接.http://www.codeproject.com/Articles/12092/Encrypt-Decrypt-Files-in-VB-NET-Using-Rijndael

Imports System
Imports System.IO
Imports System.Security
Imports System.Security.Cryptography


'*************************
'** Global Variables
'*************************

Dim strFileToEncrypt As String
Dim strFileToDecrypt As String
Dim strOutputEncrypt As String
Dim strOutputDecrypt As String
Dim fsInput As System.IO.FileStream
Dim fsOutput As System.IO.FileStream



'*************************
'** Create A Key
'*************************

Private Function CreateKey(ByVal strPassword As String) As Byte()
    'Convert strPassword to an array and store in chrData.
    Dim chrData() As Char = strPassword.ToCharArray
    'Use intLength to get strPassword size.
    Dim intLength As Integer = chrData.GetUpperBound(0)
    'Declare bytDataToHash and make it the same size as chrData.
    Dim bytDataToHash(intLength) As Byte

    'Use For Next to convert and store chrData into bytDataToHash.
    For i As Integer = 0 To chrData.GetUpperBound(0)
        bytDataToHash(i) = CByte(Asc(chrData(i)))
    Next

    'Declare what hash to use.
    Dim SHA512 As New System.Security.Cryptography.SHA512Managed
    'Declare bytResult, Hash bytDataToHash and store it in bytResult.
    Dim bytResult As Byte() = SHA512.ComputeHash(bytDataToHash)
    'Declare bytKey(31).  It will hold 256 bits.
    Dim bytKey(31) As Byte

    'Use For Next to put a specific size (256 bits) of 
    'bytResult into bytKey. The 0 To 31 will put the first 256 bits
    'of 512 bits into bytKey.
    For i As Integer = 0 To 31
        bytKey(i) = bytResult(i)
    Next

    Return bytKey 'Return the key.
End Function


'*************************
'** Create An IV
'*************************

Private Function CreateIV(ByVal strPassword As String) As Byte()
    'Convert strPassword to an array and store in chrData.
    Dim chrData() As Char = strPassword.ToCharArray
    'Use intLength to get strPassword size.
    Dim intLength As Integer = chrData.GetUpperBound(0)
    'Declare bytDataToHash and make it the same size as chrData.
    Dim bytDataToHash(intLength) As Byte

    'Use For Next to convert and store chrData into bytDataToHash.
    For i As Integer = 0 To chrData.GetUpperBound(0)
        bytDataToHash(i) = CByte(Asc(chrData(i)))
    Next

    'Declare what hash to use.
    Dim SHA512 As New System.Security.Cryptography.SHA512Managed
    'Declare bytResult, Hash bytDataToHash and store it in bytResult.
    Dim bytResult As Byte() = SHA512.ComputeHash(bytDataToHash)
    'Declare bytIV(15).  It will hold 128 bits.
    Dim bytIV(15) As Byte

    'Use For Next to put a specific size (128 bits) of bytResult into bytIV.
    'The 0 To 30 for bytKey used the first 256 bits of the hashed password.
    'The 32 To 47 will put the next 128 bits into bytIV.
    For i As Integer = 32 To 47
        bytIV(i - 32) = bytResult(i)
    Next

    Return bytIV 'Return the IV.
End Function

加密和解密

'****************************
'** Encrypt/Decrypt File
'****************************

Private Enum CryptoAction
    'Define the enumeration for CryptoAction.
    ActionEncrypt = 1
    ActionDecrypt = 2
End Enum

Private Sub EncryptOrDecryptFile(ByVal strInputFile As String, _
                                 ByVal strOutputFile As String, _
                                 ByVal bytKey() As Byte, _
                                 ByVal bytIV() As Byte, _
                                 ByVal Direction As CryptoAction)
    Try 'In case of errors.

        'Setup file streams to handle input and output.
        fsInput = New System.IO.FileStream(strInputFile, FileMode.Open, _
                                              FileAccess.Read)
        fsOutput = New System.IO.FileStream(strOutputFile, _
                                               FileMode.OpenOrCreate, _
                                               FileAccess.Write)
        fsOutput.SetLength(0) 'make sure fsOutput is empty

        'Declare variables for encrypt/decrypt process.
        Dim bytBuffer(4096) As Byte 'holds a block of bytes for processing
        Dim lngBytesProcessed As Long = 0 'running count of bytes processed
        Dim lngFileLength As Long = fsInput.Length 'the input file's length
        Dim intBytesInCurrentBlock As Integer 'current bytes being processed
        Dim csCryptoStream As CryptoStream
        'Declare your CryptoServiceProvider.
        Dim cspRijndael As New System.Security.Cryptography.RijndaelManaged
        'Setup Progress Bar
        pbStatus.Value = 0
        pbStatus.Maximum = 100

        'Determine if ecryption or decryption and setup CryptoStream.
        Select Case Direction
            Case CryptoAction.ActionEncrypt
                csCryptoStream = New CryptoStream(fsOutput, _
                cspRijndael.CreateEncryptor(bytKey, bytIV), _
                CryptoStreamMode.Write)

            Case CryptoAction.ActionDecrypt
                csCryptoStream = New CryptoStream(fsOutput, _
                cspRijndael.CreateDecryptor(bytKey, bytIV), _
                CryptoStreamMode.Write)
        End Select

        'Use While to loop until all of the file is processed.
        While lngBytesProcessed < lngFileLength
            'Read file with the input filestream.
            intBytesInCurrentBlock = fsInput.Read(bytBuffer, 0, 4096)
            'Write output file with the cryptostream.
            csCryptoStream.Write(bytBuffer, 0, intBytesInCurrentBlock)
            'Update lngBytesProcessed
            lngBytesProcessed = lngBytesProcessed + _
                                    CLng(intBytesInCurrentBlock)
            'Update Progress Bar
            pbStatus.Value = CInt((lngBytesProcessed / lngFileLength) * 100)
        End While

        'Close FileStreams and CryptoStream.
        csCryptoStream.Close()
        fsInput.Close()
        fsOutput.Close()

我已将主要代码粘贴到此处.

Answer 1

如上所述,没有什么是不可能破解的,你只能遵循最佳实践,尽可能地让任何潜在的攻击者尽可能地努力.

实际上,您链接的代码不再被视为最先进的代码(如果它曾经是).它通过散列密码来创建对称加密密钥.这很糟糕,因为密码通常没有足够的熵来阻止基于字典的复杂攻击.此外,它不使用任何盐或等效物,因此使用预先计算的表来攻击它很容易.

无论何时,您都应该使用安全的PRNG(伪随机数生成器)生成对称密钥.如果没有特别需要涉及密码,请不要这样做.如果绝对必须是密码,请使用PKCS5中的 PBKDF2 或bcrypt或scrypt等替代品.

IV也应始终从安全的PRNG生成,并且如果可能,永远不会重复使用.也没有必要从密码中派生出来,如您链接的示例所示.IV是公共信息,这意味着你可以安全地发布它-但它是强制性的,它保持不可预知的和随机的-否则,你很容易受到一些专门的攻击,除非你正在使用的认证加密模式,例如GCM.

如果您不熟悉这些主题并且有疑问,我强烈建议咨询专家.如果要保护的数据与您说的一样重要,那么应该花费额外的资金.如果没有在该地区的经验,可能是太高,你可能会忽略手工制作自己的解决方案时的重要事项.