Overview

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Using the Crypto library you can encrypt and decrypt data with a specified key.

The Crypto library uses the Crypto API methods.

You must supply the same PassPhrase string when you encrypt and decrypt the data.

A 128 bit hash object is created from the PassPhrase (using the MD5 algorithm), and from that object a 40 bit crypto key is generated.

The PassPhrase string should not be saved inside the code (as string).

Example: (you can download this example from Basic4ppc site)

'Crypto is a Crypto object and Bit is a Bitwise object

Sub Globals

      Dim string(0) as Byte, secret(0) as Byte

      PassPhrase = "my key" 'This is not recommended in real applications!!!   

End Sub

Sub App_Start

      Form1.Show

      Bit.New1

      Crypto.New1

End Sub

Sub btnEncrypt_Click

      string() = Bit.StringToBytes(txtString.Text,0,StrLength(txtString.Text)) 'Convert the string to an array of bytes.

      secret() = Crypto.Encrypt(PassPhrase, string()) 'Save the encrypted data.

      for i = 0 to ArrayLen(secret())-1 'Show the encrypted data in the TextBox

            s = s & bit.DecToHex(secret(i))

      next

      txtString.Text = s

End Sub

Sub btnDecrypt_Click

      string() = Crypto.Decrypt(PassPhrase,secret()) 'Decrypt the data.

      txtString.Text = Bit.BytesToString(string(),0,ArrayLen(string())) 'Convert the array to a string.

End Sub