ARC4 Encryption (ARCFOUR)

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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.

Dim crypt As New Chilkat.Crypt2()

Dim success As Boolean
success = crypt.UnlockComponent("Anything for 30-day trial")
If (success <> true) Then
    MsgBox("Crypt component unlock failed")
    Exit Sub
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:

Dim cipherText As String
Dim plainText As String

'  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")
TextBox1.Text = TextBox1.Text & cipherText & vbCrLf
TextBox1.Refresh()
plainText = crypt.DecryptStringENC(cipherText)
TextBox1.Text = TextBox1.Text & plainText & vbCrLf
TextBox1.Refresh()

' ARC4( "Wiki", "pedia" ) == 1021BF0420
crypt.KeyLength = 32
crypt.SetEncodedKey("Wiki","ascii")
cipherText = crypt.EncryptStringENC("pedia")
TextBox1.Text = TextBox1.Text & cipherText & vbCrLf
TextBox1.Refresh()
plainText = crypt.DecryptStringENC(cipherText)
TextBox1.Text = TextBox1.Text & plainText & vbCrLf
TextBox1.Refresh()

' ARC4( "Secret", "Attack at dawn" ) == 45A01F645FC35B383552544B9BF5
crypt.KeyLength = 48
crypt.SetEncodedKey("Secret","ascii")
cipherText = crypt.EncryptStringENC("Attack at dawn")
TextBox1.Text = TextBox1.Text & cipherText & vbCrLf
TextBox1.Refresh()
plainText = crypt.DecryptStringENC(cipherText)
TextBox1.Text = TextBox1.Text & plainText & vbCrLf
TextBox1.Refresh()

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