Generate RSA Key and Sign a String

Download Chilkat RSA ActiveX

Demonstrates how to generate a new RSA public/private key pair and use it to generate a signature for a string. The (binary) digital signature is returned as a hexidecimalized string.

Dim rsa As New ChilkatRsa

'  Any string argument automatically begins the 30-day trial.
Dim success As Long
success = rsa.UnlockComponent("30-day trial")
If (success <> 1) Then
    MsgBox "RSA component unlock failed"
    Exit Sub
End If

'  Generate a 1024-bit RSA key pair.
rsa.GenerateKey 1024

'  This example will sign a string, and receive the signature
'  in a hex-encoded string.  Therefore, set the encoding mode
'  to "hex":
rsa.EncodingMode = "hex"

Dim strData As String
strData = "This is the string to be signed."

'  Sign the string using the  md5 hash algorithm.
'  Other valid choices are "md2" and "sha-1".
Dim hexSig As String
hexSig = rsa.SignStringENC(strData,"md5")

Text1.Text = Text1.Text & hexSig & vbCrLf
Text1.Text = Text1.Text & rsa.LastErrorText & vbCrLf

'  Now verify the signature:
success = rsa.VerifyStringENC(strData,"md5",hexSig)
If (success = 1) Then
    MsgBox "Signature verified!"
Else
    Text1.Text = Text1.Text & rsa.LastErrorText & vbCrLf
End If

'  Try it with an invalid signature:
success = rsa.VerifyStringENC(strData,"md5","not a valid sig")
If (success = 1) Then
    MsgBox "Signature verified!"
Else
    Text1.Text = Text1.Text & rsa.LastErrorText & vbCrLf
End If

'  Try it with invalid data:
success = rsa.VerifyStringENC("Not the original data","md5",hexSig)
If (success = 1) Then
    MsgBox "Signature verified!"
Else
    Text1.Text = Text1.Text & rsa.LastErrorText & vbCrLf
End If

'  Try it with the wrong hash algorithm:
success = rsa.VerifyStringENC(strData,"sha-1",hexSig)
If (success = 1) Then
    MsgBox "Signature verified!"
Else
    Text1.Text = Text1.Text & rsa.LastErrorText & vbCrLf
End If