(Excel) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

Download Excel Class Modules Chilkat Excel Class Modules

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

Dim pkey As Chilkat.PrivateKey
Set pkey = Chilkat.NewPrivateKey

' Load the private key from an RSA PEM file:

success = pkey.LoadPkcs8EncryptedFile("raul_privateKey.key","a0123456789")

' Get the private key in XML format:
pkeyXml = pkey.GetXml()

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

' Import the private key into the RSA component:
success = rsa.ImportPrivateKey(pkeyXml)
If (success <> True) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' 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"


strData = "This is the string to be signed."

' Sign the string using the sha-1 hash algorithm.
' Other valid choices are "md2" and "md5".

hexSig = rsa.SignStringENC(strData,"sha-1")

Debug.Print hexSig

' Now verify with the public key.
' This example shows how to use the public key from 
' a digital certificate (.cer file)
Dim cert As Chilkat.Cert
Set cert = Chilkat.NewCert
success = cert.LoadFromFile("raul_publicKey.cer")
If (success <> True) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

Set pubKey = cert.ExportPublicKey()

' Get the private key in XML format:
pubKeyXml = pubKey.GetXml()

Dim rsa2 As Chilkat.Rsa
Set rsa2 = Chilkat.NewRsa
success = rsa2.ImportPublicKey(pubKeyXml)
If (success <> True) Then
    Debug.Print rsa2.LastErrorText
    Exit Sub
End If

' Verify the signature against the original data:
rsa2.EncodingMode = "hex"
success = rsa2.VerifyStringENC(strData,"sha-1",hexSig)
If (success <> True) Then
    Debug.Print rsa2.LastErrorText
    Exit Sub
End If

Debug.Print "Signature verified!"

' Verify with incorrect data:
success = rsa2.VerifyStringENC("something else","sha-1",hexSig)
If (success <> True) Then
    Debug.Print "Signature not verified! (which was expected in this case)"
Else
    Debug.Print "Hmmm... that's not right..."
End If