Xbase++

Create and Verify an Opaque PKCS7/CMS Signature

See more Digital Signatures Examples

Demonstrates how 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 oPrivKey
LOCAL cPassword
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 PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
//  This example will load the certificate from a .crt and the private key from a .key file

oCert := CreateObject("Chilkat.Cert")
//  The LoadFromFile method will automatically detect the format and load it.
nSuccess := oCert:LoadFromFile("qa_data/certs/test_12345678a.cer")
IF (nSuccess != 1)
    ? oCert:LastErrorText
    oCrypt:destroy()
    oCert:destroy()
    RETURN
ENDIF

//  Our private key is in an encrypted PKCS8 format.
//  If you don't know the format of your key, but you do know it's encrypted,
//  and requires a password, then just call any of the Chilkat methods that load
//  a private key w/ a password argument.  Chilkat will auto-detect the format
//  and load it correctly even if it's not the format indicated by the method name..
oPrivKey := CreateObject("Chilkat.PrivateKey")
cPassword := "12345678a"
nSuccess := oPrivKey:LoadPkcs8EncryptedFile("qa_data/certs/test_12345678a.key", cPassword)
IF (nSuccess != 1)
    ? oPrivKey:LastErrorText
    oCrypt:destroy()
    oCert:destroy()
    oPrivKey:destroy()
    RETURN
ENDIF

//  Set properties required for signing.

//  Tell it to use the cert and private key we've loaded.
nSuccess := oCrypt:SetSigningCert2(oCert, oPrivKey)
IF (nSuccess != 1)
    ? oCrypt:LastErrorText
    oCrypt:destroy()
    oCert:destroy()
    oPrivKey: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()
    oPrivKey: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")

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

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