DataFlex

ECDSA Sign Data and Get Raw R and S Values

See more ECC Examples

Demonstrates getting the raw R and S value of an ECDSA signature. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoCrypt
    String sHash1
    Variant vPrivKey
    Handle hoPrivKey
    Variant vPrng
    Handle hoPrng
    Handle hoEcdsa
    String sEcdsaSigBase64
    Handle hoAsn
    Handle hoXml
    Handle hoBd
    String r
    String s
    String sTemp1
    Integer iTemp1
    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(cComChilkatCrypt2)) To hoCrypt
    If (Not(IsComObjectCreated(hoCrypt))) Begin
        Send CreateComObject of hoCrypt
    End
    Set ComHashAlgorithm Of hoCrypt To "SHA256"
    Set ComCharset Of hoCrypt To "utf-8"
    Set ComEncodingMode Of hoCrypt To "base64"

    // Hash a string.
    Get ComHashStringENC Of hoCrypt "The quick brown fox jumps over the lazy dog" To sHash1
    Showln "hash1 = " sHash1

    // -----------------------------------------------------------
    // 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-----

    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

    // Sign the hash..
    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
    Get pvComObject of hoPrivKey to vPrivKey
    Get pvComObject of hoPrng to vPrng
    Get ComSignHashENC Of hoEcdsa sHash1 "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

    // The ECDSA signature is ASN.1 that contains a sequence of 2 large integers (r and s)
    // For example:
    // SEQUENCE (2 elem)
    //   INTEGER (255 bit) 792134D9B4AD82D5431ED03835A88E2596EB35E5B13054BD9B05A0069281ACC9
    //   INTEGER (255 bit) 481E758CC1E3CBF825537EC3D9A2CA627E5FAD1137BBEA65DF38658DCB0A9ED5

    Showln "Base64 ECDSA signature = " sEcdsaSigBase64

    // If the raw R and S values are needed, here's how to get them:
    Get Create (RefClass(cComChilkatAsn)) To hoAsn
    If (Not(IsComObjectCreated(hoAsn))) Begin
        Send CreateComObject of hoAsn
    End
    Get ComLoadEncoded Of hoAsn sEcdsaSigBase64 "base64" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoAsn To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // The R and X will be in hexidecimal in the XML.
    Get Create (RefClass(cComChilkatXml)) To hoXml
    If (Not(IsComObjectCreated(hoXml))) Begin
        Send CreateComObject of hoXml
    End
    Get ComAsnToXml Of hoAsn To sTemp1
    Get ComLoadXml Of hoXml sTemp1 To iSuccess
    Get ComGetXml Of hoXml To sTemp1
    Showln sTemp1

    // The XML looks like this:
    // <sequence>
    // <int>792134D9B4AD82D5431ED03835A88E2596EB35E5B13054BD9B05A0069281ACC9</int>
    // <int>481E758CC1E3CBF825537EC3D9A2CA627E5FAD1137BBEA65DF38658DCB0A9ED5</int>
    // </sequence>

    // Copy raw R and S hex values into a Chilkat BinData object.
    Get Create (RefClass(cComChilkatBinData)) To hoBd
    If (Not(IsComObjectCreated(hoBd))) Begin
        Send CreateComObject of hoBd
    End
    Get ComGetChildContent Of hoXml "int[0]" To r
    Get ComGetChildContent Of hoXml "int[1]" To s
    Get ComAppendEncoded Of hoBd r "hex" To iSuccess
    Get ComAppendEncoded Of hoBd s "hex" To iSuccess

    Get ComNumBytes Of hoBd To iTemp1
    Showln "Number of bytes in bd: " iTemp1


End_Procedure