(VB.NET) RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

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Demonstrates how RSA sign the utf-8 byte representation of a string to get the signature in base64 format.

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' Assuming the smartcard/USB token is installed with the correct drivers from the manufacturer,
' this code can work on multiple platforms including Windows, MacOS, Linux, and iOS.

' Chilkat automatically detects and determines the way in which the HSM is used,
' which can be by PKCS11, Apple Keychain, Microsoft CNG / Crypto API, or ScMinidriver.

Dim cert As New Chilkat.Cert

' Set the token/smartcard PIN prior to loading.
cert.SmartCardPin = "123456"

' Specify the certificate by its common name.
Dim success As Boolean = cert.LoadFromSmartcard("cn=chilkat-rsa-2048")
If (success = False) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If



Debug.WriteLine("Signing with cert: " & cert.SubjectCN)

' Create a string to be hashed and signed.
Dim sb As New Chilkat.StringBuilder
Dim crlfLineEnding As Boolean = True
Dim i As Integer
For i = 0 To 10
    sb.AppendLine("This is a test.",crlfLineEnding)
Next

Dim rsa As New Chilkat.Rsa

' Use the certificate's private key for signing.
success = rsa.SetX509Cert(cert,True)
If (success = False) Then
    Debug.WriteLine(rsa.LastErrorText)
    Exit Sub
End If


' Sign the SHA-256 hash of the utf-8 byte representation of the contents of sb
' Return the signature in base64 format.
rsa.EncodingMode = "base64"
rsa.Charset = "utf-8"
Dim stringToSign As String = sb.GetAsString()
Dim sigBase64 As String = rsa.SignStringENC(stringToSign,"sha256")
If (rsa.LastMethodSuccess = False) Then
    Debug.WriteLine(rsa.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("RSA signature as base64: " & sigBase64)