Lianja

Verify the RSA Signature of a SHA256 Hash

See more RSA Examples

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

llSuccess = .F.

// 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("CkPublicKey")
llSuccess = loPubKey.LoadFromFile("rsaPubKey.pem")
if (llSuccess = .F.) then
    ? loPubKey.LastErrorText
    release loPubKey
    return
endif

loRsa = createobject("CkRsa")

// Get the public key.
llSuccess = loRsa.UsePublicKey(loPubKey)
if (llSuccess = .F.) then
    ? loRsa.LastErrorText
    release loPubKey
    release loRsa
    return
endif

// Get the 32-byte SHA256 hash.
loBdHash = createobject("CkBinData")
llSuccess = loBdHash.LoadFile("myHash.sha256")
if (llSuccess = .F.) then
    ? "Failed to load SHA256 hash."
    release loPubKey
    release loRsa
    release loBdHash
    return
endif

// Get the RSA signature to be validated.
loBdSig = createobject("CkBinData")
llSuccess = loBdSig.LoadFile("mySig.sig")
if (llSuccess = .F.) then
    ? "Failed to load RSA signature."
    release loPubKey
    release loRsa
    release loBdHash
    release loBdSig
    return
endif

// Verify the signature against the SHA256 hash.
lcEnc = "base64"
loRsa.EncodingMode = lcEnc
llSuccess = loRsa.VerifyHashENC(loBdHash.GetEncoded(lcEnc),"sha256",loBdSig.GetEncoded(lcEnc))
if (llSuccess = .F.) then
    ? loRsa.LastErrorText
    release loPubKey
    release loRsa
    release loBdHash
    release loBdSig
    return
endif

? "Signature validated."


release loPubKey
release loRsa
release loBdHash
release loBdSig