B4X

Duplicate .NET's Rfc2898DeriveBytes Functionality

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Demonstrates how to duplicate the results produced by .NET's System.Security.Cryptography.Rfc2898DeriveBytes class. B4X

'  This example assumes Chilkat Crypt2 to have been previously unlocked.
'  See Unlock Crypt2 for sample code.

'  This example demonstrates how to duplicate the results produced
'  by .NET's System.Security.Cryptography.Rfc2898DeriveBytes class.

'  For example, here is C# code that transforms a password string into
'  bytes that can be used as a secret key for symmetric encryption (such as AES, blowfish, 3DES, etc.)
'  
'      Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes("secret", System.Text.Encoding.UTF8.GetBytes("saltsalt123"), numIterations);
'      byte[] secretKeyBytes = deriveBytes.GetBytes(numBytes);

'  (The Rfc2898DeriveBytes computation is really just the PBKDF2 algorithm with SHA-1 hashing.)
'  In Chilkat, this is what we do to match...

'  First, let's get a test vector with known results.  Both Chilkat AND Microsoft should produce
'  the same results.  RFC 6070 has some PBKDF2 HMAC-SHA1 Test Vectors.  Here is one of them:

'       Input:
'         P = "passwordPASSWORDpassword" (24 octets)
'         S = "saltSALTsaltSALTsaltSALTsaltSALTsalt" (36 octets)
'         c = 4096
'         dkLen = 25
'  
'       Output:
'         DK = 3d 2e ec 4f e4 1c 84 9b
'              80 c8 d8 36 62 c0 e4 4a
'              8b 29 1a 96 4c f2 f0 70
'              38                      (25 octets)
'  
'  

Dim crypt As ChilkatCrypt2
crypt.Initialize("crypt")

Dim salt As String = "saltSALTsaltSALTsaltSALTsaltSALTsalt"
'  Given that the salt is really binary data (can be any random bunch of bytes),
'  we must pass the exact hex string representation of the salt bytes.
'  In this case, we're getting the utf-8 byte representation of our salt string,
'  which is identical to the us-ascii byte representation because there are no 8bit chars..
Dim saltHex As String = crypt.EncodeString(salt, "utf-8", "hex")

'  Duplicate the test vector as shown above.
Dim dkHex As String = crypt.Pbkdf2("passwordPASSWORDpassword", "utf-8", "sha1", saltHex, 4096, 25 * 8, "hex")
Log(dkHex)