Encyption and Decyption of Password using VB.NET

Posted by VIJI Monday, June 29, 2009

Code to Encrypt Password
Public Function EncryptPassword(ByVal Password As String) As String
'Encrypt the Password
Dim sEncryptedPassword As String = ""
Dim sEncryptKey As String = "P@SSW@RD@09"

Try
sEncryptedPassword = EncryptDecryptClass.EncryptMD5(Password, sEncryptKey)

Catch ex As Exception
Return sEncryptedPassword
End Try

Return sEncryptedPassword
End Function

Code to Decrypt Password

Public Function DecryptPassword(ByVal Password As String) As String
'Encrypt the Password
Dim sDecryptedPassword As String = ""
Dim sEncryptKey As String = "P@SSW@RD@09"

Try
sDecryptedPassword = EncryptDecryptClass.DecryptMD5(Password, sEncryptKey)

Catch ex As Exception
Return sDecryptedPassword
End Try

Return sDecryptedPassword
End Function


EncryptDecryptClass

Imports System.Security.Cryptography

Public Class EncryptDecryptClass


'---- DECLARE SOME CONSTANTS
Private Shared m_strPassPhrase As String = "MyPriv@Password!$$" '---- any text string is good here
Private Shared m_strHashAlgorithm As String = "MD5" '--- we are doing MD5 encryption - can be "SHA1"
Private Shared m_strPasswordIterations As Integer = 2 '--- can be any number
Private Shared m_strInitVector As String = "@1B2c3D4e5F6g7H8" '--- must be 16 bytes
Private Shared m_intKeySize As Integer = 256 '--- can be 192 or 128


Friend Shared Function EncryptMD5(ByVal plainText As String, ByVal p_strSaltValue As String) As String

Dim strReturn As String = String.Empty

' Convert strings into byte arrays.
' Let us assume that strings only contain ASCII codes.
' If strings include Unicode characters, use Unicode, UTF7, or UTF8
' encoding.

Try
Dim initVectorBytes As Byte()
initVectorBytes = System.Text.Encoding.ASCII.GetBytes(m_strInitVector)

Dim saltValueBytes As Byte()
saltValueBytes = System.Text.Encoding.ASCII.GetBytes(p_strSaltValue)

' Convert our plaintext into a byte array.
' Let us assume that plaintext contains UTF8-encoded characters.
Dim plainTextBytes As Byte()
plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText)

' 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 Rfc2898DeriveBytes

password = New Rfc2898DeriveBytes(m_strPassPhrase, _
saltValueBytes, _
m_strPasswordIterations)

' 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()
Dim intKeySize As Integer = 0

intKeySize = CType((m_intKeySize / 8), Integer)

keyBytes = password.GetBytes(intKeySize)

' Create uninitialized Rijndael encryption object.
Dim symmetricKey As System.Security.Cryptography.RijndaelManaged
symmetricKey = New System.Security.Cryptography.RijndaelManaged

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

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

' Define memory stream which will be used to hold encrypted data.
Dim memoryStream As System.IO.MemoryStream
memoryStream = New System.IO.MemoryStream

' Define cryptographic stream (always use Write mode for encryption).
Dim cryptoStream As System.Security.Cryptography.CryptoStream
cryptoStream = New System.Security.Cryptography.CryptoStream(memoryStream, _
encryptor, _
System.Security.Cryptography.CryptoStreamMode.Write)
' Start encrypting.
cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length)

' Finish encrypting.
cryptoStream.FlushFinalBlock()

' Convert our encrypted data from a memory stream into a byte array.
Dim cipherTextBytes As Byte()
cipherTextBytes = memoryStream.ToArray()

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

' Convert encrypted data into a base64-encoded string.
Dim cipherText As String
cipherText = Convert.ToBase64String(cipherTextBytes)

' Return encrypted string.
strReturn = cipherText

Catch ex As Exception
strReturn = Nothing
End Try

Return strReturn

End Function

Friend Shared Function DecryptMD5(ByVal cipherText As String, ByVal p_strSaltValue As String) As String

Dim strReturn As String = String.Empty

' 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.

Try

Dim initVectorBytes As Byte()
initVectorBytes = System.Text.Encoding.ASCII.GetBytes(m_strInitVector)

Dim saltValueBytes As Byte()
saltValueBytes = System.Text.Encoding.ASCII.GetBytes(p_strSaltValue)

' Convert our ciphertext into a byte array.
Dim cipherTextBytes As Byte()
cipherTextBytes = 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 Rfc2898DeriveBytes

password = New Rfc2898DeriveBytes(m_strPassPhrase, _
saltValueBytes, _
m_strPasswordIterations)

' 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()
Dim intKeySize As Integer

intKeySize = CType((m_intKeySize / 8), Integer)

keyBytes = password.GetBytes(intKeySize)

' Create uninitialized Rijndael encryption object.
Dim symmetricKey As System.Security.Cryptography.RijndaelManaged
symmetricKey = New System.Security.Cryptography.RijndaelManaged

' It is reasonable to set encryption mode to Cipher Block Chaining
' (CBC). Use default options for other symmetric key parameters.
symmetricKey.Mode = System.Security.Cryptography.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 System.Security.Cryptography.ICryptoTransform
decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes)

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

' Define memory stream which will be used to hold encrypted data.
Dim cryptoStream As System.Security.Cryptography.CryptoStream
cryptoStream = New System.Security.Cryptography.CryptoStream(memoryStream, _
decryptor, _
System.Security.Cryptography.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()
ReDim plainTextBytes(cipherTextBytes.Length)

' Start decrypting.
Dim decryptedByteCount As Integer
decryptedByteCount = 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
plainText = System.Text.Encoding.UTF8.GetString(plainTextBytes, _
0, _
decryptedByteCount)

' Return decrypted string.
strReturn = plainText

Catch ex As Exception
strReturn = Nothing
End Try

Return strReturn


End Function

End Class

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