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POEncryption compatibility between Obj-C and VB.Net
 

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  1. POEncryption compatibility between Obj-C and VB.Net
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    <p>There are about 100,000 different possible ways to encrypt a string. Using standards like AES, CBC, and PKCS7 make things easier - but there are still problems with IVs. Salts, Encoding, etc. (As noted on <a href="https://crypto.stackexchange.com/questions/3022/what-is-the-difference-between-these-aes-encryption-methods">www.Crypto.Stackexchange.com</a>)</p> <p>For my iOS project (Obj-C), I'm using the <a href="https://github.com/dev5tec/FBEncryptor" rel="nofollow noreferrer">FBEncryptor project</a> which is an easy and well documented way to encrypt strings. However, I need code that will be able to decrypt that iOS AES string generated by FBEncryptor on a Windows platform - preferably VB.NET.</p> <p>I have yet to find another project for VB.NET that is compatible with FBEncryptor.</p> <p><strong>Does anyone know of any VB.NET encryption projects that work with FBEncryptor? If not, then what do I need to do to make the Rijndael Managed library (provided by Microsoft) work with FBEncryptor?</strong></p> <p>My VB.NET Code using <a href="http://msdn.microsoft.com/en-us/library/system.security.cryptography.rijndaelmanaged.aspx" rel="nofollow noreferrer">Rijndael Managed</a>:</p> <pre><code>Imports System.Security Imports System.Security.Cryptography Imports System.IO Imports System.Runtime.InteropServices Imports System.Text.RegularExpressions Imports System.Text Module Encrypt2 Public saltBytes As Byte() Dim hashAlgorithm As String = "SHA1" Public Sub GenerateSalt() ' Define min and max salt sizes. Dim minSaltSize As Integer Dim maxSaltSize As Integer minSaltSize = 8 maxSaltSize = 8 ' Generate a random number for the size of the salt. Dim random As Random random = New Random() Dim saltSize As Integer saltSize = random.Next(minSaltSize, maxSaltSize) ' Allocate a byte array, which will hold the salt. saltBytes = New Byte(saltSize - 1) {} ' Initialize a random number generator. Dim rng As RNGCryptoServiceProvider rng = New RNGCryptoServiceProvider() ' Fill the salt with cryptographically strong byte values. rng.GetNonZeroBytes(saltBytes) End Sub Public Function Encrypt(ByVal plainText As String, ByVal keyword As String) As String Dim hashAlgorithm As String = "SHA1" Dim passwordIterations As Integer = 128 Dim initVector As String = "@7781157e2629b09" Dim keySize As Integer = 256 Dim initVectorBytes As Byte() = Encoding.ASCII.GetBytes(initVector) Dim plainTextBytes As Byte() = Encoding.ASCII.GetBytes(plainText) GenerateSalt() Dim password As New Rfc2898DeriveBytes(keyword, saltBytes, 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.Clear() Dim cipherText As String = Convert.ToBase64String(cipherTextBytes) Return (cipherText) End Function Public Function Decrypt(ByVal cipherText As String, ByVal keyword As String) As String Dim hashAlgorithm As String = "SHA1" Dim passwordIterations As Integer = 128 Dim initVector As String = "@7781157e2629b09" 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) ' Convert the Ciphertext into a Byte array Dim cipherTextBytes As Byte() = Encoding.ASCII.GetBytes(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 GenerateSalt() Dim password As New Rfc2898DeriveBytes(keyword, saltBytes, 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 user 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 the decrypted string Return (plainText) End Function End Module </code></pre> <p>You'll notice that the IV is static and that the password iterations are low. This is because I'm not sure how to generate the IV in the same method as FBEncryptor. You may also notice that when attempting to decrypt, there are problems with the byte length.</p> <p>Any help will be appreciated! Thanks!</p>
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    1. COCan you show us the Obj-C code you use to encrypt the string?
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    2. COThe Obj-C code is available at the following GitHub Project: https://github.com/dev5tec/FBEncryptor
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    3. COYeah, I saw their code. But I was curious how you were calling it from your program. There seem to be at least two sets of API's there, and it will make a difference which one you are calling.
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