(Excel) RSA Sign String using Private Key of Certificate Type A3 (smart card / token)

Demonstrates RSA signing a string using the private key of a certificate type A3 (smart card, token).

Note: This is a Windows-only example.

Download Excel Class Modules Chilkat Excel Class Modules

'  First get the A3 certificate that was installed on the Windows system.
Dim certStore As Chilkat.CertStore
Set certStore = Chilkat.NewCertStore


thumbprint = "12c1dd8015f3f03f7b1fa619dc24e2493ca8b4b2"

'  This is specific to Windows because it is opening the Windows Current-User certificate store.

bReadOnly = True

success = certStore.OpenCurrentUserStore(bReadOnly)
If (success <> True) Then
    Debug.Print certStore.LastErrorText
    Exit Sub
End If

'  Find the certificate with the desired thumbprint
'  (There are many ways to locate a certificate.  This example chooses to find by thumbprint.)

Set cert = certStore.FindCertBySha1Thumbprint(thumbprint)
If (certStore.LastMethodSuccess <> True) Then
    Debug.Print "Failed to find the certificate."
    Exit Sub
End If

Debug.Print "Found: "; cert.SubjectCN

Dim rsa As Chilkat.Rsa
Set rsa = Chilkat.NewRsa

'  Provide the cert's private key

bUsePrivateKey = True
success = rsa.SetX509Cert(cert,bUsePrivateKey)

If (success <> True) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

'  Return the RSA signature in base64 encoded form.
rsa.EncodingMode = "base64"

'  Sign the utf-8 byte representation of the string.
rsa.Charset = "utf-8"

'  You can also choose other hash algorithms, such as SHA-1.

sigBase64 = rsa.SignStringENC("text to sign","SHA-256")
If (rsa.LastMethodSuccess <> True) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

Debug.Print "Base64 signature: "; sigBase64