Visual FoxPro

Verfies an RSA Signature

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Verifies an RSA signature against the original data. Visual FoxPro

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

lnSuccess = 0

* The following data was signed by the following example:
* RSA Sign using a Private Key on a USB Token or Smartcard
loBd = CreateObject('Chilkat.BinData')

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

* Load the signature
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.
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

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

* 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