PureBasic

ECDSA Sign Data and Verify Signature

See more ECC Examples

Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature. PureBasic

IncludeFile "CkEcc.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkPrng.pb"
IncludeFile "CkPublicKey.pb"
IncludeFile "CkCrypt2.pb"

Procedure ChilkatExample()

    success.i = 0

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

    ; To create an ECDSA signature, the data first needs to be hashed.  Then the hash
    ; is signed.

    ; Use Chilkat Crypt2 to generate a hash for any of the following
    ; hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

    crypt.i = CkCrypt2::ckCreate()
    If crypt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkCrypt2::setCkHashAlgorithm(crypt, "SHA256")
    CkCrypt2::setCkCharset(crypt, "utf-8")
    CkCrypt2::setCkEncodingMode(crypt, "base64")

    ; Hash a string.
    hash1.s = CkCrypt2::ckHashStringENC(crypt,"The quick brown fox jumps over the lazy dog")
    Debug "hash1 = " + hash1

    ; Or hash a file..
    hash2.s = CkCrypt2::ckHashFileENC(crypt,"qa_data/hamlet.xml")
    Debug "hash2 = " + hash2

    ; (The Crypt2 API provides many other ways to hash data..)

    ; -----------------------------------------------------------
    ; An ECDSA private key is used for signing.  The public key is for signature verification.
    ; Load our ECC private key.
    ; Our private key file contains this:

    ; 	// -----BEGIN PRIVATE KEY-----
    ; 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
    ; 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
    ; 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
    ; 	-----END PRIVATE KEY-----

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

    success = CkPrivateKey::ckLoadPemFile(privKey,"qa_data/ecc/secp256r1-key-pkcs8.pem")
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(privKey)
        CkCrypt2::ckDispose(crypt)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    ; We'll need a PRNG source for random number generation.
    ; Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
    prng.i = CkPrng::ckCreate()
    If prng.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

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

    ecdsaSigBase64.s = CkEcc::ckSignHashENC(ecdsa,hash1,"base64",privKey,prng)
    If CkEcc::ckLastMethodSuccess(ecdsa) <> 1
        Debug CkEcc::ckLastErrorText(ecdsa)
        CkCrypt2::ckDispose(crypt)
        CkPrivateKey::ckDispose(privKey)
        CkPrng::ckDispose(prng)
        CkEcc::ckDispose(ecdsa)
        ProcedureReturn
    EndIf

    Debug "ECDSA signature = " + ecdsaSigBase64

    ; -----------------------------------------------------------
    ; Now let's verify the signature using the public key.

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

    success = CkPublicKey::ckLoadFromFile(pubKey,"qa_data/ecc/secp256r1-pubkey.pem")
    If success <> 1
        Debug CkPublicKey::ckLastErrorText(pubKey)
        CkCrypt2::ckDispose(crypt)
        CkPrivateKey::ckDispose(privKey)
        CkPrng::ckDispose(prng)
        CkEcc::ckDispose(ecdsa)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf

    result.i = CkEcc::ckVerifyHashENC(ecdsa,hash1,ecdsaSigBase64,"base64",pubKey)
    If result = 1
        Debug "Signature is valid."
        CkCrypt2::ckDispose(crypt)
        CkPrivateKey::ckDispose(privKey)
        CkPrng::ckDispose(prng)
        CkEcc::ckDispose(ecdsa)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf

    If result = 0
        Debug "Signature is invalid."
        CkCrypt2::ckDispose(crypt)
        CkPrivateKey::ckDispose(privKey)
        CkPrng::ckDispose(prng)
        CkEcc::ckDispose(ecdsa)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf

    If result < 0
        Debug CkEcc::ckLastErrorText(ecdsa)
        Debug "The VerifyHashENC method call failed."
        CkCrypt2::ckDispose(crypt)
        CkPrivateKey::ckDispose(privKey)
        CkPrng::ckDispose(prng)
        CkEcc::ckDispose(ecdsa)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf



    CkCrypt2::ckDispose(crypt)
    CkPrivateKey::ckDispose(privKey)
    CkPrng::ckDispose(prng)
    CkEcc::ckDispose(ecdsa)
    CkPublicKey::ckDispose(pubKey)


    ProcedureReturn
EndProcedure