From 918f2ac2942e8f882b60debc97e2e55fb4e045f6 Mon Sep 17 00:00:00 2001
From: Christian Grothoff
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. +
+In Taler terminology, we distinguish between + transactions where the exclusive ownership of the value of a + coin is passed from one entity to another, and sharing + 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. +
+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 fresh coins (of a total value + of 3 Euros) that are unlinkable to the original 5 Euro coin + to ensure privacy. To ensure that the resulting refresh + operation where the change is converted to fresh coins cannot be + used to transfer 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 link to the private + information of the fresh coins generated by the operation. As a + result of this trick, refresh operations cannot uses to create + transfers, as the linkage ensures that the fresh coins are + always shared with the owner of the original coin. +
+As a result, Taler does not intrude into the + personal economic domain, offers good privacy, taxability + for transactions and the ability to give change. +
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