PureBasic

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.

PureBasic

IncludeFile "CkBinData.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkPrng.pb"
IncludeFile "CkPublicKey.pb"
IncludeFile "CkEcc.pb"

Procedure ChilkatExample()

    success.i = 0

    ; 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.
    privKey.i = CkPrivateKey::ckCreate()
    If privKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPrivateKey::ckLoadEncryptedPemFile(privKey,"qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret")
    If success = 0
        Debug CkPrivateKey::ckLastErrorText(privKey)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    ; Load some data to be signed.
    bd.i = CkBinData::ckCreate()
    If bd.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkBinData::ckLoadFile(bd,"qa_data/hamlet.xml")
    If success = 0
        Debug "Failed to load file to be hashed."
        CkPrivateKey::ckDispose(privKey)
        CkBinData::ckDispose(bd)
        ProcedureReturn
    EndIf

    ecdsa.i = CkEcc::ckCreate()
    If ecdsa.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    prng.i = CkPrng::ckCreate()
    If prng.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
    Debug "ECDSA signing the sha256 hash of the data..."
    sig.s = CkEcc::ckSignBd(ecdsa,bd,"sha256","base64",privKey,prng)
    Debug "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.
    pubKey.i = CkPublicKey::ckCreate()
    If pubKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPublicKey::ckLoadFromFile(pubKey,"qa_data/ecc/secp256r1-pub.pem")
    If success = 0
        Debug CkPublicKey::ckLastErrorText(pubKey)
        CkPrivateKey::ckDispose(privKey)
        CkBinData::ckDispose(bd)
        CkEcc::ckDispose(ecdsa)
        CkPrng::ckDispose(prng)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf

    ecc2.i = CkEcc::ckCreate()
    If ecc2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    result.i = CkEcc::ckVerifyBd(ecc2,bd,"sha256",sig,"base64",pubKey)
    If result <> 1
        Debug CkEcc::ckLastErrorText(ecc2)
        CkPrivateKey::ckDispose(privKey)
        CkBinData::ckDispose(bd)
        CkEcc::ckDispose(ecdsa)
        CkPrng::ckDispose(prng)
        CkPublicKey::ckDispose(pubKey)
        CkEcc::ckDispose(ecc2)
        ProcedureReturn
    EndIf

    Debug "Verified!"

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

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

    sig = CkEcc::ckSignBd(ecdsa,bd,"sha384","base64",privKey,prng)
    Debug "sig = " + sig

    result = CkEcc::ckVerifyBd(ecc2,bd,"sha384",sig,"base64",pubKey)
    If result <> 1
        Debug CkEcc::ckLastErrorText(ecc2)
        CkPrivateKey::ckDispose(privKey)
        CkBinData::ckDispose(bd)
        CkEcc::ckDispose(ecdsa)
        CkPrng::ckDispose(prng)
        CkPublicKey::ckDispose(pubKey)
        CkEcc::ckDispose(ecc2)
        ProcedureReturn
    EndIf

    Debug "Verified!"


    CkPrivateKey::ckDispose(privKey)
    CkBinData::ckDispose(bd)
    CkEcc::ckDispose(ecdsa)
    CkPrng::ckDispose(prng)
    CkPublicKey::ckDispose(pubKey)
    CkEcc::ckDispose(ecc2)


    ProcedureReturn
EndProcedure