Xbase++

A3/A4 Certificate to Create and Verify an Opaque PKCS7/CMS Signature

See more Digital Signatures Examples

Demonstrates how to use an A3 or A4 certificate w/ private key on a smartcard or token to create a PKCS7 opaque signature, and also how to verify an opaque signature.

An opaque signature is different than a detached PKCS7 signature in that it contains the original data. Verifying an opaque signature retrieves the original content.

Xbase++

LOCAL nSuccess
LOCAL oCrypt
LOCAL oCert
LOCAL cOriginalData
LOCAL cOpaqueSig
LOCAL oVCrypt
LOCAL cExtractedData

nSuccess := 0

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

oCrypt := CreateObject("Chilkat.Crypt2")

//  A certificate and private key is needed to create a signature.
//  Chilkat provides many different ways to load a certificate and private key, such
//  as from a smartcards and hardware tokens, PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
//  This example will load the default certificate from the smartcard that is currently in
//  the smartcard reader.

oCert := CreateObject("Chilkat.Cert")

//  If the smartcard or token requires a PIN, we can set it here to avoid the dialog...
oCert:SmartCardPin := "000000"

nSuccess := oCert:LoadFromSmartcard("")
IF (nSuccess != 1)
    ? oCert:LastErrorText
    oCrypt:destroy()
    oCert:destroy()
    RETURN
ENDIF

//  Tell it to use the cert and private key we've loaded.
nSuccess := oCrypt:SetSigningCert(oCert)
IF (nSuccess != 1)
    ? oCrypt:LastErrorText
    oCrypt:destroy()
    oCert:destroy()
    RETURN
ENDIF

//  Indicate we want the opaque signature in base64 format:
oCrypt:EncodingMode := "base64"

//  Sign the string using the "utf-8" byte representation:
oCrypt:Charset := "utf-8"

//  Create the opaque signature:
cOriginalData := "This is the string to be signed."
cOpaqueSig := oCrypt:OpaqueSignStringENC(cOriginalData)
IF (oCrypt:LastMethodSuccess != 1)
    ? oCrypt:LastErrorText
    oCrypt:destroy()
    oCert:destroy()
    RETURN
ENDIF

? cOpaqueSig

//  The output looks like this:
//  MIIPgQYJKoZIhvcNAQcCoIIPcjCCD24CAQExCzAJBgUrDgMCGgUAMC8GCSqGSIb3DQEHAaAiBCBUaGlzIGlzIHRoZSBzdHJpbmcgdG8gYmUgc...

//  ----------------------------------------------------------------------------------------------
//  Now let's verify the signature and retrieve the original data.
//  We'll use a new Crypt2 object to keep things completely separate...

oVCrypt := CreateObject("Chilkat.Crypt2")

//  We only need the certificate to verify a signature (and extract the data from
//  an opaque signature).  The public key is always embedded within a certificate.
nSuccess := oVCrypt:SetVerifyCert(oCert)
IF (nSuccess != 1)
    ? oVCrypt:LastErrorText
    oCrypt:destroy()
    oCert:destroy()
    oVCrypt:destroy()
    RETURN
ENDIF

oVCrypt:EncodingMode := "base64"
oVCrypt:Charset := "utf-8"

cExtractedData := oVCrypt:OpaqueVerifyStringENC(cOpaqueSig)
IF (oVCrypt:LastMethodSuccess != 1)
    ? oVCrypt:LastErrorText
    oCrypt:destroy()
    oCert:destroy()
    oVCrypt:destroy()
    RETURN
ENDIF

? "The extracted data: " + cExtractedData

//  The output is:
//  The extracted data: This is the string to be signed.

oCrypt:destroy()
oCert:destroy()
oVCrypt:destroy()