(Visual FoxPro) Verfies an RSA Signature

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Verifies an RSA signature against the original data.

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

LOCAL loBd
LOCAL i
LOCAL loBdSig
LOCAL lnSuccess
LOCAL loPubKey
LOCAL loRsa

* The following data was signed by the following example:
* RSA Sign using a Private Key on a USB Token or Smartcard
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBd = CreateObject('Chilkat.BinData')

FOR i = 0 TO 100
    loBd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex")
NEXT

* Load the signature
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdSig = CreateObject('Chilkat.BinData')
lnSuccess = loBdSig.LoadFile("rsaSignatures/test1.sig")
IF (lnSuccess = 0) THEN
    ? "Failed to load the RSA signature"
    RELEASE loBd
    RELEASE loBdSig
    CANCEL
ENDIF

* Get the public key to be used for signature verification.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.PublicKey')
loPubKey = CreateObject('Chilkat.PublicKey')
lnSuccess = loPubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
IF (lnSuccess = 0) THEN
    ? loPubKey.LastErrorText
    RELEASE loBd
    RELEASE loBdSig
    RELEASE loPubKey
    CANCEL
ENDIF

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Rsa')
loRsa = CreateObject('Chilkat.Rsa')
loRsa.ImportPublicKeyObj(loPubKey)

* Verify the hash of the data against the signature.
* We pass in the original data.  Internally, the hash is generated
* and used to validate the signature.
* Validating the RSA signature means two things:  
* (1) the original data is exactly what was signed, and 
* (2) it was signed by the owner of the RSA private key.
lnSuccess = loRsa.VerifyBd(loBd,"sha256",loBdSig)

IF (lnSuccess = 0) THEN
    ? loRsa.LastErrorText
    ? "Signature invalid."
ELSE
    ? "Signature valid."
ENDIF

RELEASE loBd
RELEASE loBdSig
RELEASE loPubKey
RELEASE loRsa