DataFlex

Create ECSDA Signature using Raw r and s Format (not ASN.1)

See more ECC Examples

Demonstrates how to create an ECDSA signature using the raw r/s format.

ECDSA signatures have two equal sized parts, r and s. There are two common formats for encoding the signature:

(a) Concatenating the raw byte array of r and s
(b) Encoding both into a structured ASN.1 / DER sequence.

This example demonstrates how to create a signature that is a byte array of r and s concatenated.

Note: This example requires Chilkat v9.5.0.97 or greater.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoSb
    String sHash
    Variant vPrivKey
    Handle hoPrivKey
    Variant vPrng
    Handle hoPrng
    Handle hoEcdsa
    String sEcdsaSigBase64
    Variant vPubKey
    Handle hoPubKey
    Integer iResult
    String sTemp1
    Boolean bTemp1

    Move False To iSuccess

    // 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.

    Get Create (RefClass(cComChilkatStringBuilder)) To hoSb
    If (Not(IsComObjectCreated(hoSb))) Begin
        Send CreateComObject of hoSb
    End
    Get ComAppend Of hoSb "The quick brown fox jumps over the lazy dog" To iSuccess
    Get ComGetHash Of hoSb "sha256" "base64" "utf-8" To sHash

    // Load the ECDSA key to be used for signing.
    Get Create (RefClass(cComChilkatPrivateKey)) To hoPrivKey
    If (Not(IsComObjectCreated(hoPrivKey))) Begin
        Send CreateComObject of hoPrivKey
    End
    Get ComLoadPemFile Of hoPrivKey "qa_data/ecc/secp256r1-key-pkcs8.pem" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoPrivKey To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get Create (RefClass(cComChilkatPrng)) To hoPrng
    If (Not(IsComObjectCreated(hoPrng))) Begin
        Send CreateComObject of hoPrng
    End
    Get Create (RefClass(cComChilkatEcc)) To hoEcdsa
    If (Not(IsComObjectCreated(hoEcdsa))) Begin
        Send CreateComObject of hoEcdsa
    End

    // Produce a signature that is not ASN.1, but is instead the concatenation
    // of the raw r and s signature parts.
    // This feature was added in Chilkat v9.5.0.97
    Set ComAsnFormat Of hoEcdsa To False

    Get pvComObject of hoPrivKey to vPrivKey
    Get pvComObject of hoPrng to vPrng
    Get ComSignHashENC Of hoEcdsa sHash "base64" vPrivKey vPrng To sEcdsaSigBase64
    Get ComLastMethodSuccess Of hoEcdsa To bTemp1
    If (bTemp1 <> True) Begin
        Get ComLastErrorText Of hoEcdsa To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "ECDSA signature = " sEcdsaSigBase64

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

    Get Create (RefClass(cComChilkatPublicKey)) To hoPubKey
    If (Not(IsComObjectCreated(hoPubKey))) Begin
        Send CreateComObject of hoPubKey
    End
    Get ComLoadFromFile Of hoPubKey "qa_data/ecc/secp256r1-pubkey.pem" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoPubKey To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Note: When verifying, Chilkat will auto-detect the format for both kinds of ECDSA signatures (ASN.1 or binary r+s)
    Get pvComObject of hoPubKey to vPubKey
    Get ComVerifyHashENC Of hoEcdsa sHash sEcdsaSigBase64 "base64" vPubKey To iResult
    If (iResult = 1) Begin
        Showln "Signature is valid."
        Procedure_Return
    End

    If (iResult = 0) Begin
        Showln "Signature is invalid."
        Procedure_Return
    End

    If (iResult < 0) Begin
        Get ComLastErrorText Of hoEcdsa To sTemp1
        Showln sTemp1
        Showln "The VerifyHashENC method call failed."
        Procedure_Return
    End



End_Procedure