(Visual FoxPro) 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.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loCert
LOCAL loPrivKey
LOCAL loJwsProtHdr
LOCAL loJws
LOCAL lnSignatureIndex
LOCAL lnBIncludeBom
LOCAL lcPayloadStr
LOCAL lcJwsCompact
LOCAL loJws2
LOCAL loRsaPubKey
LOCAL v
LOCAL loJoseHeader

lnSuccess = 0

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

* Load the certificate from a smart card.
loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadFromSmartcard("")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loCert
    CANCEL
ENDIF

* 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).

* If the associated private key was present on the smartcard, then you can simply
* get it from the Chilkat cert object:
loPrivKey = CreateObject('Chilkat.PrivateKey')
lnSuccess = loCert.GetPrivateKey(loPrivKey)
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loCert
    RELEASE loPrivKey
    CANCEL
ENDIF

* You can check the key type to make sure it's RSA.
* This will output "rsa" if the key is RSA.
? "Key type = " + loPrivKey.KeyType

* Create the JWS Protected Header
loJwsProtHdr = CreateObject('Chilkat.JsonObject')
loJwsProtHdr.AppendString("alg","RS256")

loJws = CreateObject('Chilkat.Jws')

* Set the protected header:
lnSignatureIndex = 0
loJws.SetProtectedHeader(lnSignatureIndex,loJwsProtHdr)

* Set the RSA key:
loJws.SetPrivateKey(lnSignatureIndex,loPrivKey)

* Set the payload.
lnBIncludeBom = 0
lcPayloadStr = "In our village, folks say God crumbles up the old moon into stars."
loJws.SetPayload(lcPayloadStr,"utf-8",lnBIncludeBom)

* Create the JWS
* By default, the compact serialization is used.
lcJwsCompact = loJws.CreateJws()
IF (loJws.LastMethodSuccess = 0) THEN
    ? loJws.LastErrorText
    RELEASE loCert
    RELEASE loPrivKey
    RELEASE loJwsProtHdr
    RELEASE loJws
    CANCEL
ENDIF

? "JWS: " + lcJwsCompact

* 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.
loJws2 = CreateObject('Chilkat.Jws')

* Load the JWS.
lnSuccess = loJws2.LoadJws(lcJwsCompact)

loRsaPubKey = CreateObject('Chilkat.PublicKey')
loPrivKey.ToPublicKey(loRsaPubKey)

* Set the RSA public key used for validation.
lnSignatureIndex = 0
loJws2.SetPublicKey(lnSignatureIndex,loRsaPubKey)

* Validate the 1st (and only) signature at index 0..
v = loJws2.Validate(lnSignatureIndex)
IF (v < 0) THEN
    * Perhaps Chilkat was not unlocked or the trial expired..
    ? "Method call failed for some other reason."
    ? loJws2.LastErrorText
    RELEASE loCert
    RELEASE loPrivKey
    RELEASE loJwsProtHdr
    RELEASE loJws
    RELEASE loJws2
    RELEASE loRsaPubKey
    CANCEL
ENDIF

IF (v = 0) THEN
    ? "Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both."
    RELEASE loCert
    RELEASE loPrivKey
    RELEASE loJwsProtHdr
    RELEASE loJws
    RELEASE loJws2
    RELEASE loRsaPubKey
    CANCEL
ENDIF

* If we get here, the signature was validated..
? "Signature validated."

* Recover the original content:
? loJws2.GetPayload("utf-8")

* Examine the protected header:

loJoseHeader = CreateObject('Chilkat.JsonObject')
lnSuccess = loJws2.GetProtectedH(lnSignatureIndex,loJoseHeader)
IF (lnSuccess = 0) THEN
    ? loJws2.LastErrorText
    RELEASE loCert
    RELEASE loPrivKey
    RELEASE loJwsProtHdr
    RELEASE loJws
    RELEASE loJws2
    RELEASE loRsaPubKey
    RELEASE loJoseHeader
    CANCEL
ENDIF

loJoseHeader.EmitCompact = 0

? "Protected (JOSE) header:"
? loJoseHeader.Emit()

* Output:

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

RELEASE loCert
RELEASE loPrivKey
RELEASE loJwsProtHdr
RELEASE loJws
RELEASE loJws2
RELEASE loRsaPubKey
RELEASE loJoseHeader