(Unicode C++) Generate ECDSA Key and Get Details as XML

Demonstrates how to generate an ECDSA key and gets the parts as XML.

Note: This example requires Chilkat v11.0.0 or greater.

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#include <CkEccW.h>
#include <CkPrngW.h>
#include <CkPrivateKeyW.h>
#include <CkAsnW.h>
#include <CkXmlW.h>
#include <CkCrypt2W.h>

void ChilkatSample(void)
    {
    // This requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkEccW ecc;

    // Generate a random ECC private key on the secp256k1 curve.
    // Chilkat also supports other curves, such as secp384r1, secp521r1, and secp256r1.

    // Create a Fortuna PRNG and seed it with system entropy.
    // This will be our source of random data for generating the ECC private key.
    CkPrngW fortuna;
    const wchar_t *entropy = fortuna.getEntropy(32,L"base64");
    bool success = fortuna.AddEntropy(entropy,L"base64");

    CkPrivateKeyW privKey;
    success = ecc.GenKey(L"secp256k1",fortuna,privKey);
    if (success != true) {
        wprintf(L"%s\n",ecc.lastErrorText());
        return;
    }

    // An EC private key has this ASN.1
    // ECPrivateKey ::= SEQUENCE {
    //     version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
    //     privateKey     OCTET STRING,
    //     parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
    //     publicKey  [1] BIT STRING OPTIONAL (This is the ANSI X9.63 public key format.)

    CkAsnW asn;
    success = asn.LoadEncoded(privKey.getPkcs1ENC(L"base64"),L"base64");
    if (success != true) {
        wprintf(L"%s\n",asn.lastErrorText());
        return;
    }

    CkXmlW xml;
    xml.LoadXml(asn.asnToXml());

    wprintf(L"%s\n",xml.getXml());

    // The XML looks like this:
    // <?xml version="1.0" encoding="utf-8" ?>
    // <sequence>
    //     <int>01</int>
    //     <octets>JgJvBG+3wletkJab8iXAkpz0O8/AgWZSpkYVcB7SpnU=</octets>
    //     <contextSpecific tag="0" constructed="1">
    //         <oid>1.3.132.0.10</oid>
    //     </contextSpecific>
    // </sequence>

    // The 32-byte private key is in the octets..
    // Get it as hex.
    CkCrypt2W crypt;
    const wchar_t *privKeyHex = crypt.reEncode(xml.getChildContent(L"octets"),L"base64",L"hex");

    wprintf(L"EC private key as hex = %s\n",privKeyHex);
    }