Visual FoxPro Requires Chilkat v11.0.0+

RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

See more Digital Signatures Examples

Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256. Visual FoxPro

LOCAL lnSuccess
LOCAL loCrypt
LOCAL loPfx
LOCAL loCert
LOCAL lcOriginalText
LOCAL lcPkcs7sig
LOCAL lcOpaqueSig
LOCAL lcOrigTxt

lnSuccess = 0

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

loCrypt = CreateObject('Chilkat.Crypt2')

*  Get a digital certificate with private key from a .pfx
*  (Chilkat has many different ways to provide a cert + private key for siging.
*  Using a PFX is just one possible option.)
loPfx = CreateObject('Chilkat.Pfx')
lnSuccess = loPfx.LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD")
IF (lnSuccess = 0) THEN
    ? loPfx.LastErrorText
    RELEASE loCrypt
    RELEASE loPfx
    CANCEL
ENDIF

*  Get the certificate to be used for signing.
*  (The typical case for a PFX is that it contains a cert with an associated private key,
*  as well as other certificates in the chain of authentication.  The cert with the private
*  key should be in the first position at index 0.)

loCert = CreateObject('Chilkat.Cert')
lnSuccess = loPfx.CertAt(0,loCert)
IF (lnSuccess = 0) THEN
    ? loPfx.LastErrorText
    RELEASE loCrypt
    RELEASE loPfx
    RELEASE loCert
    CANCEL
ENDIF

loCrypt.SetSigningCert(loCert)

*  Indicate that RSASSA-PSS with SHA256 should be used.
loCrypt.SigningAlg = "pss"
loCrypt.HashAlgorithm = "sha256"

loCrypt.EncodingMode = "base64"

*  Sign a string and return the base64 PKCS7 detached signature
lcOriginalText = "This is a test"
lcPkcs7sig = loCrypt.SignStringENC(lcOriginalText)
? "Detached Signature:"
? lcPkcs7sig

*  This signature looks like this:
*  MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

*  The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
*  then copy-and-paste the Base64 signature into the form and decode..

*  The signature can be verified against the original data like this:
lnSuccess = loCrypt.VerifyStringENC(lcOriginalText,lcPkcs7sig)
? "Signature verified: " + STR(lnSuccess)
lnSuccess = loCrypt.VerifyStringENC("Not the original text",lcPkcs7sig)
? "Signature verified: " + STR(lnSuccess)

*  Now we'll create an opaque signature (the opposite of a detached signature). 
*  An opaque signature is a PKCS7 message that contains both the original data and
*  the signature.  The verification process extracts the original data.
lcOpaqueSig = loCrypt.OpaqueSignStringENC(lcOriginalText)
? "Opaque Signature:"
? lcOpaqueSig

*  The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
*  then copy-and-paste the Base64 signature into the form and decode..

*  We can verify and extract the original data:
lcOrigTxt = loCrypt.OpaqueVerifyStringENC(lcOpaqueSig)
IF (loCrypt.LastMethodSuccess <> 1) THEN
    ? "Signature verification failed."
    ? loCrypt.LastErrorText
    RELEASE loCrypt
    RELEASE loPfx
    RELEASE loCert
    CANCEL
ENDIF

? "Signature verified."
? "Extracted text:" + lcOrigTxt

RELEASE loCrypt
RELEASE loPfx
RELEASE loCert