explain transaction vs. sharing

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+         <h2 lang="en" id="taxability">Taler technology: About taxability, change and privacy</h1>
+         <h2 lang="de">Taler Technik: Steuern, Wechselgeld und Privatsph&auml;re</h1>
+         <h2 lang="fr" note="outdated"></h2>
+         <h2 lang="it" note="outdated"></h2>
+         <p lang="en">One of the key goals of Taler is to provide anonymity for
+           citizens buying goods and services, while ensuring that the state can
+           observe incoming transactions to ensure businesses engage only in
+           legal activities and do not evade taxes (such as income tax,
+           sales tax or value-added tax).  However, we also want to stay
+           out of the immediate personal domain, so sharing funds within a
+           family or copying coins between devices should not be subject to
+           monitoring by the state.
+         </p>
+         <p lang="en">In Taler terminology, we distinguish between
+           <b>transactions</b> where the exclusive ownership of the value of a
+           coin is passed from one entity to another, and <b>sharing</b>
+           whereafter control over a coin is shared by multiple electronic
+           wallets (which may belong to different individuals).  In Taler,
+           the receiver of a transaction is visible to the state and thus
+           can be taxed, while sharing is invisible to anyone not involved.
+           Once a coin is shared among different individuals, any one of those
+           can try to spend it, but only the first spender would succeed. Thus,
+           sharing requires a strong trust relationship among the individuals
+           involved, and thus represent interactions in the protected immediate
+           personal domain, and not commercial transactions.
+         </p>
+         <p lang="en">When Taler needs to provide change, for example because
+           a customer only has a 5 Euro coin but wants to make a 2 Euro
+           purchase, it needs to create <b>fresh</b> coins (of a total value
+           of 3 Euros) that are <b>unlinkable</b> to the original 5 Euro coin
+           to ensure privacy.  To ensure that the resulting <b>refresh</b>
+           operation where the change is converted to fresh coins cannot be
+           used to <i>transfer</i> funds from one entity to another, Taler ensures
+           that any owner of an original coin that was involved in a
+           refresh operation can follow a <b>link</b> to the private
+           information of the fresh coins generated by the operation.  As a
+           result of this trick, refresh operations cannot uses to create
+           <i>transfers</i>, as the linkage ensures that the fresh coins are
+           always <i>shared</i> with the owner of the original coin.
+         </p>
+         <p lang="en">As a result, Taler does not intrude into the
+           personal economic domain, offers good privacy, taxability
+           for transactions and the ability to give change.
+         </p>
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