(Lianja) ECDSA Sign and Verify Data using Different Hash Algorithms

Demonstrates how to create ECDSA signatures on data using different hash algorithms.

Note: This example requires Chilkat v9.5.0.85 or greater because the SignBd and VerifyBd methods were added in v9.5.0.85.

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

// First load an ECDSA private key to be used for signing.
loPrivKey = createobject("CkPrivateKey")
llSuccess = loPrivKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret")
if (llSuccess = .F.) then
    ? loPrivKey.LastErrorText
    release loPrivKey
    return
endif

// Load some data to be signed.
loBd = createobject("CkBinData")
llSuccess = loBd.LoadFile("qa_data/hamlet.xml")
if (llSuccess = .F.) then
    ? "Failed to load file to be hashed."
    release loPrivKey
    release loBd
    return
endif

loEcdsa = createobject("CkEcc")
loPrng = createobject("CkPrng")

// Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
? "ECDSA signing the sha256 hash of the data..."
lcSig = loEcdsa.SignBd(loBd,"sha256","base64",loPrivKey,loPrng)
? "sig = " + lcSig

// Verify the signature against the original data.
// (We must use the same hash algorithm that was used when signing.)

// Load the public key that corresponds to the private key used for signing.
loPubKey = createobject("CkPublicKey")
llSuccess = loPubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem")
if (llSuccess = .F.) then
    ? loPubKey.LastErrorText
    release loPrivKey
    release loBd
    release loEcdsa
    release loPrng
    release loPubKey
    return
endif

loEcc2 = createobject("CkEcc")
lnResult = loEcc2.VerifyBd(loBd,"sha256",lcSig,"base64",loPubKey)
if (lnResult <> 1) then
    ? loEcc2.LastErrorText
    release loPrivKey
    release loBd
    release loEcdsa
    release loPrng
    release loPubKey
    release loEcc2
    return
endif

? "Verified!"

// ----------------------------------------------------------------------------------------
// Let's do the same thing, but with sha384 hashing...

? "--------------------------------------------"
? "ECDSA signing the sha384 hash of the data..."

lcSig = loEcdsa.SignBd(loBd,"sha384","base64",loPrivKey,loPrng)
? "sig = " + lcSig

lnResult = loEcc2.VerifyBd(loBd,"sha384",lcSig,"base64",loPubKey)
if (lnResult <> 1) then
    ? loEcc2.LastErrorText
    release loPrivKey
    release loBd
    release loEcdsa
    release loPrng
    release loPubKey
    release loEcc2
    return
endif

? "Verified!"


release loPrivKey
release loBd
release loEcdsa
release loPrng
release loPubKey
release loEcc2