(VB.NET) Generate RSA Key and Sign a String

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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.

Note: This example requires Chilkat v11.0.0 or greater.

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Chilkat .NET Framework

Chilkat for .NET Core

Dim success As Boolean = False

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim rsa As New Chilkat.Rsa

' Generate a 2048-bit RSA key.
Dim privKey As New Chilkat.PrivateKey
success = rsa.GenKey(2048,privKey)

rsa.UsePrivateKey(privKey)

' Return the signature in hex.
rsa.EncodingMode = "hex"

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

' Sign the SHA256 hash of the string.
Dim hexSig As String = rsa.SignStringENC(strData,"sha256")

Debug.WriteLine(hexSig)

' Now verify the signature:
Dim pubKey As New Chilkat.PublicKey
privKey.ToPublicKey(pubKey)
rsa.UsePublicKey(pubKey)

success = rsa.VerifyStringENC(strData,"sha256",hexSig)
If (success = True) Then
    Debug.WriteLine("Signature verified!")
Else
    Debug.WriteLine(rsa.LastErrorText)
End If


' Try it with an invalid signature:
success = rsa.VerifyStringENC(strData,"sha256","not a valid sig")
If (success = True) Then
    Debug.WriteLine("Signature verified!")
Else
    Debug.WriteLine("Signature validation failed!")
End If


' Try it with invalid data:
success = rsa.VerifyStringENC("Not the original data","sha256",hexSig)
If (success = True) Then
    Debug.WriteLine("Signature verified!")
Else
    Debug.WriteLine("Signature validation failed!")
End If