const MyKey32 R  ( QByteArray::fromHex( "9ac20335eb38768d2052be1dbbc3c8f6178407458e51e6b4ad22f1d91758895b" ) );
const MyKey32 S1 ( QByteArray::fromHex( "2da94e7cb83e17d307d46c80df4f3315b17af13c4a04ef352495f1442562a290" ) );
const MyKey32 Z1 ( QByteArray::fromHex( "068fbde1dd7e06f4e88ae63a50f8ee07eff41c4b9586cbef1235b83281ab145d" ) );
const MyKey32 S2 ( QByteArray::fromHex( "43273c2390b15bbe7e4d38559b1d4e6c0d63aad2c586652ec423d851df065271" ) );
const MyKey32 Z2 ( QByteArray::fromHex( "015b14bdc6f69058bfa8dcdc0e8bcd1fc87f4303804f200bfa6aadf627a8d5f6" ) );
const MyKey20 addr ( MyKey20::of ( "14tVK2JhEPsZEL7yYzMNXDYQ6dG3FnzzEY" ) );
const MyKey32 priv ( MyKey32::getPrivateKey ( R, S1, Z1, S2, Z2, addr ) );
_trace ( priv.toHex ( ) );

const MyKey32 MyKey32::getPrivateKey ( const MyKey32& r, const MyKey32& s1, const MyKey32& z1, const MyKey32& s2, const MyKey32& z2, const MyKey20& addr )
{
  // private key = (z1*s2 - z2*s1)/(r*(s1-s2))
  [skip]
}