(Visual FoxPro) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loPrivKey
LOCAL loRsa
LOCAL lcStrData
LOCAL lcHexSig
LOCAL loCert
LOCAL loPubKey
LOCAL loRsa2

lnSuccess = 0

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

loPrivKey = CreateObject('Chilkat.PrivateKey')

* Load the private key from an RSA PEM file:
lnSuccess = loPrivKey.LoadAnyFormatFile("raul_privateKey.key","a0123456789")
IF (lnSuccess = 0) THEN
    ? loPrivKey.LastErrorText
    RELEASE loPrivKey
    CANCEL
ENDIF

loRsa = CreateObject('Chilkat.Rsa')

* Import the private key into the RSA component:
lnSuccess = loRsa.UsePrivateKey(loPrivKey)
IF (lnSuccess = 0) THEN
    ? loRsa.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    CANCEL
ENDIF

* This example will sign a string, and receive the signature
* in a hex-encoded string.  Therefore, set the encoding mode
* to "hex":
loRsa.EncodingMode = "hex"

lcStrData = "This is the string to be signed."

* Sign the string using the sha256 hash algorithm.
* Other valid choices are sha1, sha384, sha512 and others.
lcHexSig = loRsa.SignStringENC(lcStrData,"sha256")
IF (loRsa.LastMethodSuccess = 0) THEN
    ? loRsa.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    CANCEL
ENDIF

? lcHexSig

* Now verify with the public key.
* This example shows how to use the public key from 
* a digital certificate (.cer file)
loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadFromFile("raul_publicKey.cer")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    RELEASE loCert
    CANCEL
ENDIF

loPubKey = CreateObject('Chilkat.PublicKey')
loCert.GetPublicKey(loPubKey)

loRsa2 = CreateObject('Chilkat.Rsa')
lnSuccess = loRsa2.UsePublicKey(loPubKey)
IF (lnSuccess = 0) THEN
    ? loRsa2.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    RELEASE loCert
    RELEASE loPubKey
    RELEASE loRsa2
    CANCEL
ENDIF

* Verify the signature against the original data:
loRsa2.EncodingMode = "hex"
lnSuccess = loRsa2.VerifyStringENC(lcStrData,"sha256",lcHexSig)
IF (lnSuccess = 0) THEN
    ? loRsa2.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    RELEASE loCert
    RELEASE loPubKey
    RELEASE loRsa2
    CANCEL
ENDIF

? "Signature verified!"

* Verify with incorrect data:
lnSuccess = loRsa2.VerifyStringENC("something else","sha256",lcHexSig)
IF (lnSuccess <> 1) THEN
    ? "Signature not verified! (which was expected in this case)"
ELSE
    ? "Hmmm... that's not right..."
ENDIF

RELEASE loPrivKey
RELEASE loRsa
RELEASE loCert
RELEASE loPubKey
RELEASE loRsa2