(Visual FoxPro) RSA Signature/Verify with .key and .cer

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

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

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

loPrivKey = CreateObject('Chilkat_9_5_0.PrivateKey')

*  Load the private key from an RSA .key file:
lnSuccess = loPrivKey.LoadPemFile("privateKey.key")
IF (lnSuccess <> 1) THEN
    ? loPrivKey.LastErrorText
    RELEASE loPrivKey
    CANCEL
ENDIF

*  Get the private key in XML format:
lcPrivKeyXml = loPrivKey.GetXml()

loRsa = CreateObject('Chilkat_9_5_0.Rsa')

*  Any string argument automatically begins the 30-day trial.
lnSuccess = loRsa.UnlockComponent("30-day trial")
IF (lnSuccess <> 1) THEN
    ? loRsa.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    CANCEL
ENDIF

*  Import the private key into the RSA component:
lnSuccess = loRsa.ImportPrivateKey(lcPrivKeyXml)
IF (lnSuccess <> 1) THEN
    ? loRsa.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    CANCEL
ENDIF

*  Create the signature as a hex string:
loRsa.EncodingMode = "hex"

*  If some other non-Chilkat application or web service is going to be verifying
*  the signature, it is important to match the byte-ordering.
*  The LittleEndian property may be set to 1
*  for little-endian byte ordering,
*  or 0  for big-endian byte ordering.
*  Microsoft apps typically use little-endian, while
*  OpenSSL and other services (such as Amazon CloudFront)
*  use big-endian.
loRsa.LittleEndian = 0

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

*  Sign the string using the sha-1 hash algorithm.
*  Other valid choices are "md2", "sha256", "sha384",
*  "sha512", and "md5".
lcHexSig = loRsa.SignStringENC(lcStrData,"sha-1")

? lcHexSig

*  Load a digital certificate from a .cer file:
loCert = CreateObject('Chilkat_9_5_0.Cert')

lnSuccess = loCert.LoadFromFile("myCert.cer")
IF (lnSuccess <> 1) THEN
    ? loCert.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    RELEASE loCert
    CANCEL
ENDIF

loPubKey = loCert.ExportPublicKey()

*  Now verify using a separate instance of the RSA object:
loRsa2 = CreateObject('Chilkat_9_5_0.Rsa')

*  Import the public key into the RSA object:
lnSuccess = loRsa2.ImportPublicKey(loPubKey.GetXml())
IF (lnSuccess <> 1) THEN
    ? loRsa2.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    RELEASE loCert
    RELEASE loRsa2
    CANCEL
ENDIF

RELEASE loPubKey

*  The signature is a hex string, so make sure the EncodingMode is correct:
loRsa2.EncodingMode = "hex"

*  Verify the signature:
lnSuccess = loRsa2.VerifyStringENC(lcStrData,"sha-1",lcHexSig)
IF (lnSuccess <> 1) THEN
    ? loRsa2.LastErrorText
    RELEASE loPrivKey
    RELEASE loRsa
    RELEASE loCert
    RELEASE loRsa2
    CANCEL
ENDIF

? "Success."

RELEASE loPrivKey
RELEASE loRsa
RELEASE loCert
RELEASE loRsa2