B4X Requires Chilkat v11.5.0+

Create JWS Using Private Key on a Smart Card

See more JSON Web Signatures (JWS) Examples

Creates and validates a JSON Web Signature (JWS) using the private key associated with a certificate on a smart card. B4X

Dim success As Boolean = False

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

'  Load the certificate from a smart card.
Dim cert As ChilkatCert
cert.Initialize("cert")

'  Set the smarcard PIN prior to loading
cert.SmartCardPin = "123456"

'  Detect the connected smartcard or USB security token and load the default certificate.
success = cert.LoadFromSmartcard("")
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


'  Note: Chilkat provides many different ways to load a certificate from a smartcard or USB token,
'  such as selecting a certificate if the card contains multiple certificates with private keys,
'  or working with lower-level PKCS11 or ScMinidriver API's (both of which Chilkat provides).

'  Create the JWS Protected Header
Dim jwsProtHdr As ChilkatJsonObject
jwsProtHdr.Initialize

If cert.IsEcdsa = True Then
    jwsProtHdr.AppendString("alg", "ES256")
Else
    jwsProtHdr.AppendString("alg", "RS256")
End If


Dim jws As ChilkatJws
jws.Initialize

'  Set the protected header:
Dim signatureIndex As Int = 0
jws.SetProtectedHeader(signatureIndex, jwsProtHdr)

'  Provide the private key via the certificate.
'  This requires Chilkat v11.5.0 or greater.
jws.SetSigningCert(signatureIndex, cert)

'  Set the payload.
Dim bIncludeBom As Boolean = False
Dim payloadStr As String = "In our village, folks say God crumbles up the old moon into stars."
jws.SetPayload(payloadStr, "utf-8", bIncludeBom)

'  Create the JWS
'  By default, the compact serialization is used.
Dim jwsCompact As String = jws.CreateJws
If jws.LastMethodSuccess = False Then
    Log(jws.LastErrorText)
    Return
End If


Log("JWS: " & jwsCompact)

'  sample output:
'  JWS: eyJhbGciOiJQUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.TRWhwRo5dMv9-8OzrInfJTwmUGYgjLfHk8lqF072ND-FmLWEBnUTOpY8oJXp8FdWw2SalbdOeNlrtlJjwk4XK8Ql2iJ_2qMCtxsvLPhKBOqFoAF4aBvTOEDVJDxf0DaBSiydEEtfTVV2iwBcjWabu5J2XieR5y7QZQtuHsn7T3qKBvCcCejN3Y2oqAT3qMHvu1fTms1r_91wBn_K7Wjd9UkZ1n02qQcUHJznR_OF2BgN7_KWIDAF9ZS9keoju2NPpPelO4yxa2XUPnehY3G7dHKoCxUEQR4d2Xc5voqDASTVCDqQS4PVOZdvT3Ein6-SanAlCwbWBbkvT8g6-5PImQ

'  Now load the JWS, validate, and recover the original text.
Dim jws2 As ChilkatJws
jws2.Initialize

'  Load the JWS.
success = jws2.LoadJws(jwsCompact)

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

'  Set the public key used for validation.
signatureIndex = 0
jws2.SetPublicKey(signatureIndex, pubKey)

'  Validate the 1st (and only) signature at index 0..
Dim v As Int = jws2.Validate(signatureIndex)
If v < 0 Then
    '  Perhaps Chilkat was not unlocked or the trial expired..
    Log("Method call failed for some other reason.")
    Log(jws2.LastErrorText)
    Return
End If

If v = 0 Then
    Log("Invalid signature.  The key was incorrect, the JWS was invalid, or both.")
    Return
End If


'  If we get here, the signature was validated..
Log("Signature validated.")

'  Recover the original content:
Log(jws2.GetPayload("utf-8"))

'  Examine the protected header:

Dim joseHeader As ChilkatJsonObject
joseHeader.Initialize
success = jws2.GetProtectedH(signatureIndex, joseHeader)
If success = False Then
    Log(jws2.LastErrorText)
    Return
End If


joseHeader.EmitCompact = False

Log("Protected (JOSE) header:")
Log(joseHeader.Emit)

'  Output:

'  	Signature validated.
'  	In our village, folks say God crumbles up the old moon into stars.
'  	Protected (JOSE) header:
'  	{ 
'  	  "alg": "RS256"
'  	}