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Article PS01042345

HOWTO: Using "raw" symmetric encryption keys with AspEncrypt

Problem Description

A symmetric key may be provided to an application in the "raw" form, i.e. as a sequence of bits, stripped of all version, header and padding information. For example, a 128-bit RC2 key may be provided as a hex string, as follows: "1804A391BBD829605AE7DC3D30B8708B".

For AspEncrypt to use such a key for encryption or decryption, the key needs to be imported into a CryptoKey object. However, the methods Context.ImportKeyFromBlob and Context.ImportKeyFromFile only accept symmetric keys in a format generated by AspEncrypt itself, but won't allow a key in the form of a "raw" sequence of bits to be imported.

Solution

Starting with Version 2.01 , AspEncrypt is capable of importing "raw" keys via the method ImportRawKey , as follows:

Set CM = Server.CreateObject("Persits.CryptoManager")
Set Context = CM.OpenContext("", True)

Set Blob = CM.CreateBlob
Blob.Hex = "1804A391BBD829605AE7DC3D30B8708B"
Set Key = Context.ImportRawKey(Blob, calgRC2)
Key.DecryptFile "c:\file.txt.xxx", "c:\file.txt"

Created: 2/8/2002 4:49:01 AM
Last Modified: 2/9/2002 4:13:28 PM

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