(Excel) AES XTS Mode

Demonstrates the AES-XTS mode of operation.

Note: This example requires Chilkat v9.5.0.91 or greater.

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' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' Here we have a sample from CAVS validatition data:

' COUNT = 301
' DataUnitLen = 200
' Key = 
' 394c97881abd989d29c703e48a72b397
' a7acf51b59649eeea9b33274d8541df4
' i = 4b15c684a152d485fe9937d39b168c29
' PT = 2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0
' CT = f3473802e38a3ffef4d4fb8e6aa266ebde553a64528a06463e

' Note: The above sample requires an AES-XTS implementation that fully supports ciphertext-stealing
' because the data to be encrypted is not an even multiple of the AES block size (i.e. not a multiple of 16 bytes).
' Chilkat fully supports AES-XTS with ciphertext stealing.
' (i.e. Chilkat implements XEX-based tweaked-codebook mode with ciphertext stealing (XTS))


key = "394c97881abd989d29c703e48a72b397"

tweakKey = "a7acf51b59649eeea9b33274d8541df4"

dataUnit = "4b15c684a152d485fe9937d39b168c29"

Dim bd As Chilkat.BinData
Set bd = Chilkat.NewBinData
Dim success As Boolean
success = bd.AppendEncoded("2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0","hex")

Dim crypt As Chilkat.Crypt2
Set crypt = Chilkat.NewCrypt2

crypt.CryptAlgorithm = "aes"
crypt.CipherMode = "xts"
crypt.KeyLength = 128

crypt.SetEncodedKey key,"hex"
crypt.XtsSetEncodedTweakKey tweakKey,"hex"
crypt.XtsSetEncodedTweakValue dataUnit,"hex"

' In-place encrypt the contents of bd.
success = crypt.EncryptBd(bd)

Debug.Print "CT = "; bd.GetEncoded("hexlower")

' Decrypt to revert back to the unencrypted content:
success = crypt.DecryptBd(bd)

Debug.Print "PT = "; bd.GetEncoded("hexlower")

' Output:
' CT = f3473802e38a3ffef4d4fb8e6aa266ebde553a64528a06463e
' PT = 2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0