B4X

ECDSA Sign and Verify Data using Different Hash Algorithms

See more ECC Examples

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.

B4X

Dim success As Boolean = False

'  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.
Dim privKey As ChilkatPrivateKey
privKey.Initialize("privKey")
success = privKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem", "secret")
If success = False Then
    Log(privKey.LastErrorText)
    Return
End If


'  Load some data to be signed.
Dim bd As ChilkatBinData
bd.Initialize
success = bd.LoadFile("qa_data/hamlet.xml")
If success = False Then
    Log("Failed to load file to be hashed.")
    Return
End If


Dim ecdsa As ChilkatEcc
ecdsa.Initialize
Dim prng As ChilkatPrng
prng.Initialize

'  Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
Log("ECDSA signing the sha256 hash of the data...")
Dim sig As String = ecdsa.SignBd(bd, "sha256", "base64", privKey, prng)
Log("sig = " & sig)

'  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.
Dim pubKey As ChilkatPublicKey
pubKey.Initialize
success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem")
If success = False Then
    Log(pubKey.LastErrorText)
    Return
End If


Dim ecc2 As ChilkatEcc
ecc2.Initialize
Dim result As Int = ecc2.VerifyBd(bd, "sha256", sig, "base64", pubKey)
If result <> 1 Then
    Log(ecc2.LastErrorText)
    Return
End If


Log("Verified!")

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

Log("--------------------------------------------")
Log("ECDSA signing the sha384 hash of the data...")

sig = ecdsa.SignBd(bd, "sha384", "base64", privKey, prng)
Log("sig = " & sig)

result = ecc2.VerifyBd(bd, "sha384", sig, "base64", pubKey)
If result <> 1 Then
    Log(ecc2.LastErrorText)
    Return
End If


Log("Verified!")