ARC4 Encryption (ARCFOUR)

ARC4 (ARCFOUR) encryption. The Chilkat encryption component supports the ARC4 streaming encryption algorithm.

Download Chilkat Crypt ActiveX

Dim crypt As New ChilkatCrypt2

Dim success As Long
success = crypt.UnlockComponent("Anything for 30-day trial")
If (success <> 1) Then
    MsgBox "Crypt component unlock failed"
    Exit Sub
End If

'  Set the encryption algorithm = "arc4"
crypt.CryptAlgorithm = "arc4"

'  KeyLength may range from 1 byte to 256 bytes.
'  (i.e. 8 bits to 2048 bits)
'  ARC4 key sizes are typically in the range of
'  40 to 128 bits.
'  The KeyLength property is specified in bits:
crypt.KeyLength = 128

'  Note: The PaddingScheme and CipherMode properties
'  do not apply w/ ARC4.  ARC4 does not encrypt in blocks --
'  it is a streaming encryption algorithm. The number of output bytes
'  is exactly equal to the number of input bytes.

'  EncodingMode specifies the encoding of the output for
'  encryption, and the input for decryption.
'  It may be "hex", "url", "base64", or "quoted-printable".
crypt.EncodingMode = "hex"

'  Note: ARC4 does not utilize initialization vectors.  IV's only
'  apply to block encryption algorithms.

'  The secret key must equal the size of the key.
'  For 128-bit encryption, the binary secret key is 16 bytes.
Dim keyHex As String
keyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
crypt.SetEncodedKey keyHex,"hex"

'  Encrypt a string...
'  The output length is exactly equal to the input.  In this
'  example, the input string is 44 chars (ANSI bytes) so the
'  output is 44 bytes -- and when hex encoded results in an
'  88-char string (2 chars per byte for the hex encoding).
Dim encStr As String
encStr = crypt.EncryptStringENC("The quick brown fox jumps over the lazy dog.")
MsgBox encStr

'  Now decrypt:
Dim decStr As String
decStr = crypt.DecryptStringENC(encStr)
MsgBox decStr