ARC4 Encryption (ARCFOUR)

Demonstrates simple ARC4 encryption to match some simple test vectors published by Wikipedia. ARC4 is a fast stream cipher supporting key lengths from 8 to 2048 bits (i.e. from 1 to 256 bytes). It is not a block cipher, so there is no padding, no modes, and no initialization vector.

Download Chilkat Crypt ActiveX

Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
Set outFile = fso.CreateTextFile("output.txt", True)

set crypt = CreateObject("Chilkat.Crypt2")

success = crypt.UnlockComponent("Anything for 30-day trial")
If (success <> 1) Then
    MsgBox "Crypt component unlock failed"
    WScript.Quit
End If

'  Set the encryption algorithm to ARC4:
crypt.CryptAlgorithm = "arc4"

'  We want the encrypted output to be a hex-encoded string.
crypt.EncodingMode = "hex"

'  Encrypt some test vectors from Wikipedia:

'  The key length (in bits) is equal to the number of us-ascii
'  bytes in our key string * 8.

' ARC4( "Key", "Plaintext" ) == BBF316E8D940AF0AD3
crypt.KeyLength = 24
crypt.SetEncodedKey "Key","ascii"
cipherText = crypt.EncryptStringENC("Plaintext")
outFile.WriteLine(cipherText)
plainText = crypt.DecryptStringENC(cipherText)
outFile.WriteLine(plainText)

' ARC4( "Wiki", "pedia" ) == 1021BF0420
crypt.KeyLength = 32
crypt.SetEncodedKey "Wiki","ascii"
cipherText = crypt.EncryptStringENC("pedia")
outFile.WriteLine(cipherText)
plainText = crypt.DecryptStringENC(cipherText)
outFile.WriteLine(plainText)

' ARC4( "Secret", "Attack at dawn" ) == 45A01F645FC35B383552544B9BF5
crypt.KeyLength = 48
crypt.SetEncodedKey "Secret","ascii"
cipherText = crypt.EncryptStringENC("Attack at dawn")
outFile.WriteLine(cipherText)
plainText = crypt.DecryptStringENC(cipherText)
outFile.WriteLine(plainText)

'  Note: The call to SetEncodedKey serves to set the key
'  to the us-ascii bytes of the string.

outFile.Close