B4X Requires Chilkat v11.0.0+

RSA Sign with PKCS8 Encrypted Key

See more RSA Examples

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it). B4X

Dim success As Boolean = False

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

Dim privKey As ChilkatPrivateKey
privKey.Initialize("privKey")

'  Load the private key from an RSA PEM file:
success = privKey.LoadAnyFormatFile("raul_privateKey.key", "a0123456789")
If success = False Then
    Log(privKey.LastErrorText)
    Return
End If


Dim rsa As ChilkatRsa
rsa.Initialize

'  Import the private key into the RSA component:
success = rsa.UsePrivateKey(privKey)
If success = False Then
    Log(rsa.LastErrorText)
    Return
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"

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

'  Sign the string using the sha256 hash algorithm.
'  Other valid choices are sha1, sha384, sha512 and others.
Dim hexSig As String = rsa.SignStringENC(strData, "sha256")
If rsa.LastMethodSuccess = False Then
    Log(rsa.LastErrorText)
    Return
End If


Log(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 ChilkatCert
cert.Initialize("cert")
success = cert.LoadFromFile("raul_publicKey.cer")
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


Dim pubKey As ChilkatPublicKey
pubKey.Initialize
cert.GetPublicKey(pubKey)

Dim rsa2 As ChilkatRsa
rsa2.Initialize
success = rsa2.UsePublicKey(pubKey)
If success = False Then
    Log(rsa2.LastErrorText)
    Return
End If


'  Verify the signature against the original data:
rsa2.EncodingMode = "hex"
success = rsa2.VerifyStringENC(strData, "sha256", hexSig)
If success = False Then
    Log(rsa2.LastErrorText)
    Return
End If


Log("Signature verified!")

'  Verify with incorrect data:
success = rsa2.VerifyStringENC("something else", "sha256", hexSig)
If success <> True Then
    Log("Signature not verified! (which was expected in this case)")
Else
    Log("Hmmm... that's not right...")
End If