Visual FoxPro

CMS Sign Hash

Demonstrates how to use the SignHashENC method to sign a pre-computed hash. This method creates a CMS signature (PKCS7 detached signature).

This example requires Chilkat v9.5.0.90 or later.

Visual FoxPro

LOCAL lnSuccess
LOCAL loCrypt
LOCAL lcBase64Hash
LOCAL loCert
LOCAL lcBase64CmsSig

lnSuccess = 0

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

loCrypt = CreateObject('Chilkat.Crypt2')

* Create the hash to be signed...
loCrypt.HashAlgorithm = "sha256"
loCrypt.EncodingMode = "base64"
loCrypt.Charset = "utf-8"
* Create the SHA256 hash of a string using the utf-8 byte representation.
* Return the hash as base64.
lcBase64Hash = loCrypt.HashStringENC("This is the string to be hashed")

* Load a certificate for signing.
loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loCrypt
    RELEASE loCert
    CANCEL
ENDIF

loCrypt.SetSigningCert(loCert)

* Sign the hash to create a base64 CMS signature (which does not contain the original data).
* We can get the signature in a single line of base64 by specifying "base64", or 
* we can get multi-line base64 by specifying "base64_mime".
loCrypt.EncodingMode = "base64_mime"
lcBase64CmsSig = loCrypt.SignHashENC(lcBase64Hash,"sha256","base64")
IF (loCrypt.LastMethodSuccess = 0) THEN
    ? loCrypt.LastErrorText
    RELEASE loCrypt
    RELEASE loCert
    CANCEL
ENDIF

* Note: In the above call to SignHashENC, the encoding of the returned CMS signature is specified by the EncodingMode property.
* However, the encoding of the passed-in hash is indicated by the 3rd argument.

? "CMS Signature: " + lcBase64CmsSig

RELEASE loCrypt
RELEASE loCert