vb.net 如何解密 MD5 哈希

How to decrypt a MD5 hash

提问by Shafay

I have used the following function to encrypt my password:

我使用以下函数来加密我的密码：

HashPasswordForStoringInConfigFile(Password, "MD5")

Now I want to decrypt the password again.

现在我想再次解密密码。

NoteI'm showing the encrypted password in a grid-view and I want to decrypt it when the particular row goes in edit mode.

注意我在网格视图中显示加密密码，我想在特定行进入编辑模式时解密它。

回答by Heider Sati

The simple answer is "you can't"

简单的答案是“你不能”

The idea of hashing is to generate a "safe" code from the real password, where that code can be stored in clear text; in a database (or text file) somewhere where other users might be seeing it somehow.

散列的想法是从真实密码生成一个“安全”代码，该代码可以以明文形式存储；在数据库（或文本文件）中的某个地方，其他用户可能会以某种方式看到它。

When someone tries to login, your system would compute another hash from the new login and then compare with the existing hash from your existing database, if the hash matches, then you know it's the correct password and then you can allow them to login, otherwise, it's not the same password / login-failed.

当有人尝试登录时，您的系统会从新登录中计算另一个哈希值，然后与现有数据库中的现有哈希值进行比较，如果哈希值匹配，则您知道这是正确的密码，然后您可以允许他们登录，否则，这不是相同的密码/登录失败。

The reason why you cannot reverse the hash is because a hash is computed by doing the following steps:

无法反转散列的原因是因为通过执行以下步骤来计算散列：

1) Taking the password into some algorithm to: 2) Generate a very large string, then: 3) Chop that string and: 4) Take a part of it as your "hash"

1）将密码带入某种算法以：2）生成一个非常大的字符串，然后：3）切掉该字符串并：4）将其中的一部分作为您的“哈希”

So you see, even if you are superman in decoding and can figure the algorithm out, and know the hash code, and managed to reverse it back into the original form, then you would still have parts of the password missing, hence unsuccessful.

所以你看，即使你是解码的超人，可以计算出算法，知道哈希码，并设法将它反转回原始形式，那么你仍然会丢失部分密码，因此不成功。

This is why Hashes are secure.

这就是哈希是安全的原因。

I hope this explains it.

我希望这能解释它。

回答by user1797958

you can make encrypt and decrypt function like this to encrypt and decrypt your text , and further u can use as per your need to display the decrypt text here is the function

您可以像这样使用加密和解密功能来加密和解密您的文本，并且您可以根据需要使用这里显示的解密文本是该功能

Public Function Encrypt(ByVal plainText As String) As String

    Dim passPhrase As String = "yourPassPhrase"
    Dim saltValue As String = "mySaltValue"
    Dim hashAlgorithm As String = "MD5"

    Dim passwordIterations As Integer = 2
    Dim initVector As String = "@1B2c3D4e5F6g7H8"
    Dim keySize As Integer = 256

    Dim initVectorBytes As Byte() = Encoding.ASCII.GetBytes(initVector)
    Dim saltValueBytes As Byte() = Encoding.ASCII.GetBytes(saltValue)

    Dim plainTextBytes As Byte() = Encoding.UTF8.GetBytes(plainText)


    Dim password As New PasswordDeriveBytes(passPhrase, saltValueBytes, hashAlgorithm, passwordIterations)

    Dim keyBytes As Byte() = password.GetBytes(keySize \ 8)
    Dim symmetricKey As New RijndaelManaged()

    symmetricKey.Mode = CipherMode.CBC

    Dim encryptor As ICryptoTransform = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes)

    Dim memoryStream As New MemoryStream()
    Dim cryptoStream As New CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write)

    cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length)
    cryptoStream.FlushFinalBlock()
    Dim cipherTextBytes As Byte() = memoryStream.ToArray()
    memoryStream.Close()
    cryptoStream.Close()
    Dim cipherText As String = Convert.ToBase64String(cipherTextBytes)
    Return cipherText
End Function

and for decrypt use this

和解密使用这个

Public Function Decrypt(ByVal cipherText As String) As String
    Dim passPhrase As String = "yourPassPhrase"
    Dim saltValue As String = "mySaltValue"
    Dim hashAlgorithm As String = "MD5"

    Dim passwordIterations As Integer = 2
    Dim initVector As String = "@1B2c3D4e5F6g7H8"
    Dim keySize As Integer = 256
    ' Convert strings defining encryption key characteristics into byte
    ' arrays. Let us assume that strings only contain ASCII codes.
    ' If strings include Unicode characters, use Unicode, UTF7, or UTF8
    ' encoding.
    Dim initVectorBytes As Byte() = Encoding.ASCII.GetBytes(initVector)
    Dim saltValueBytes As Byte() = Encoding.ASCII.GetBytes(saltValue)

    ' Convert our ciphertext into a byte array.
    Dim cipherTextBytes As Byte() = Convert.FromBase64String(cipherText)

    ' First, we must create a password, from which the key will be 
    ' derived. This password will be generated from the specified 
    ' passphrase and salt value. The password will be created using
    ' the specified hash algorithm. Password creation can be done in
    ' several iterations.
    Dim password As New PasswordDeriveBytes(passPhrase, saltValueBytes, hashAlgorithm, passwordIterations)

    ' Use the password to generate pseudo-random bytes for the encryption
    ' key. Specify the size of the key in bytes (instead of bits).
    Dim keyBytes As Byte() = password.GetBytes(keySize \ 8)

    ' Create uninitialized Rijndael encryption object.
    Dim symmetricKey As New RijndaelManaged()

    ' It is reasonable to set encryption mode to Cipher Block Chaining
    ' (CBC). Use default options for other symmetric key parameters.
    symmetricKey.Mode = CipherMode.CBC

    ' Generate decryptor from the existing key bytes and initialization 
    ' vector. Key size will be defined based on the number of the key 
    ' bytes.
    Dim decryptor As ICryptoTransform = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes)

    ' Define memory stream which will be used to hold encrypted data.
    Dim memoryStream As New MemoryStream(cipherTextBytes)

    ' Define cryptographic stream (always use Read mode for encryption).
    Dim cryptoStream As New CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read)

    ' Since at this point we don't know what the size of decrypted data
    ' will be, allocate the buffer long enough to hold ciphertext;
    ' plaintext is never longer than ciphertext.
    Dim plainTextBytes As Byte() = New Byte(cipherTextBytes.Length - 1) {}

    ' Start decrypting.
    Dim decryptedByteCount As Integer = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length)

    ' Close both streams.
    memoryStream.Close()
    cryptoStream.Close()

    ' Convert decrypted data into a string. 
    ' Let us assume that the original plaintext string was UTF8-encoded.
    Dim plainText As String = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount)

    ' Return decrypted string.   
    Return plainText
End Function

and call the function you will get the result.

并调用您将获得结果的函数。