(Excel) RSA Sign Binary Data and Verify (Recover the Original Data)

Demonstrates how to RSA sign binary data and then verify/recover the original data.

Note: This example uses methods introduced in Chilkat v9.5.0.77.

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

' Load an RSA private key for signing.
Dim privKey As Chilkat.PrivateKey
Set privKey = Chilkat.NewPrivateKey

success = privKey.LoadEncryptedPemFile("qa_data/pem/rsa_passwd.pem","passwd")
If (success <> True) Then
    Debug.Print privKey.LastErrorText
    Exit Sub
End If

Dim rsa As Chilkat.Rsa
Set rsa = Chilkat.NewRsa
success = rsa.ImportPrivateKeyObj(privKey)

' We have some binary data (in hex) to sign

originalData = "0102030405060708090A"
Dim bd As Chilkat.BinData
Set bd = Chilkat.NewBinData
success = bd.AppendEncoded(originalData,"hex")

' If successful, the contents of bd are replaced with the RSA signature.
success = rsa.OpenSslSignBd(bd)
If (success <> True) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' Show the RSA signature in base64
Debug.Print bd.GetEncoded("base64")

' ------------------------------------------
' Get the public key from the private key

Set pubKey = privKey.GetPublicKey()

' Verify the signature and extract the original data.
Dim rsa2 As Chilkat.Rsa
Set rsa2 = Chilkat.NewRsa
success = rsa2.ImportPublicKeyObj(pubKey)


bVerified = rsa2.OpenSslVerifyBd(bd)
Debug.Print "signature verified: "; bVerified

' Show the original data:
Debug.Print "original data: "; bd.GetEncoded("hex")