(Visual FoxPro) Verify the RSA Signature of a SHA256 Hash

See more RSA Examples

Demonstrates how to verify an RSA signature of a SHA256 hash.

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

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ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loPubKey
LOCAL loRsa
LOCAL loBdHash
LOCAL loBdSig
LOCAL lcEnc

lnSuccess = 0

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

* Let's say you have a file containing the 32-bytes of a SHA256 hash,
* and a file that is an RSA signature of those 32 bytes.
* Here's how you verify using the RSA public key found in a PEM.

loPubKey = CreateObject('Chilkat.PublicKey')
lnSuccess = loPubKey.LoadFromFile("rsaPubKey.pem")
IF (lnSuccess = 0) THEN
    ? loPubKey.LastErrorText
    RELEASE loPubKey
    CANCEL
ENDIF

loRsa = CreateObject('Chilkat.Rsa')

* Get the public key.
lnSuccess = loRsa.UsePublicKey(loPubKey)
IF (lnSuccess = 0) THEN
    ? loRsa.LastErrorText
    RELEASE loPubKey
    RELEASE loRsa
    CANCEL
ENDIF

* Get the 32-byte SHA256 hash.
loBdHash = CreateObject('Chilkat.BinData')
lnSuccess = loBdHash.LoadFile("myHash.sha256")
IF (lnSuccess = 0) THEN
    ? "Failed to load SHA256 hash."
    RELEASE loPubKey
    RELEASE loRsa
    RELEASE loBdHash
    CANCEL
ENDIF

* Get the RSA signature to be validated.
loBdSig = CreateObject('Chilkat.BinData')
lnSuccess = loBdSig.LoadFile("mySig.sig")
IF (lnSuccess = 0) THEN
    ? "Failed to load RSA signature."
    RELEASE loPubKey
    RELEASE loRsa
    RELEASE loBdHash
    RELEASE loBdSig
    CANCEL
ENDIF

* Verify the signature against the SHA256 hash.
lcEnc = "base64"
loRsa.EncodingMode = lcEnc
lnSuccess = loRsa.VerifyHashENC(loBdHash.GetEncoded(lcEnc),"sha256",loBdSig.GetEncoded(lcEnc))
IF (lnSuccess = 0) THEN
    ? loRsa.LastErrorText
    RELEASE loPubKey
    RELEASE loRsa
    RELEASE loBdHash
    RELEASE loBdSig
    CANCEL
ENDIF

? "Signature validated."

RELEASE loPubKey
RELEASE loRsa
RELEASE loBdHash
RELEASE loBdSig