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text: Improve blaming section fruther
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README.md

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@@ -205,7 +205,7 @@ We make the following modifications as compared to the original SimplPedPop prop
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- Every participant holds a secret seed, from which all required random values are derived deterministically using a pseudorandom function (based on tagged hashes as defined in [[BIP 340](https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki)]).
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- Individual participants' public shares are added to the output of the DKG. This allows partial signature verification.
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- The participants send VSS commitments to an untrusted coordinator instead of directly to each other. This lets the coordinator aggregate VSS commitments, which reduces communication costs. However, if a session fails, participants are still able to investigate who provided invalid secret shares by asking the coordinator for the other participants' individual contributions to their public share.
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- The participants send VSS commitments to an untrusted coordinator instead of directly to each other. This lets the coordinator aggregate VSS commitments, which reduces communication costs. Nevertheless, if a session fails, participants are able to investigate who provided invalid secret shares by asking the coordinator for the other participants' individual contributions to their public share.
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- To prevent a malicious participant from embedding a [[BIP 341](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki)] Taproot script path in the threshold public key, the participants tweak the VSS commitment such that the corresponding threshold public key has an unspendable BIP script path.
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- ~The proofs of knowledge are not included in the data for the equality check. This will reduce the size of the backups in ChillDKG.~ (TODO: This will be fixed in an updated version of the paper.)
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@@ -584,7 +584,7 @@ and even recovered participants can participate in signing sessions.)
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### Blaming Faulty Parties
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Any faulty party can make a ChillDKG session abort by sending a message that deviates from the protocol specification.
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To help investigating and resolving these protocol failures, ChillDKG provides a *blame functionality*
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To help resolve the underlying problem, ChillDKG provides a *blame functionality*
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that enables honest protocol parties to identify and blame at least one participant suspected to be faulty:
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- If an honest participant aborts the session, then this participant will blame at least one participant or the coordinator.
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- If an honest coordinator aborts the session, then the coordinator then will blame at least one participant.
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aborts due to a timeout while waiting for a protocol message
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will trivially blame the party who is supposed to send the outstanding message.
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The aborting party will be guaranteed that the suspected party is indeed faulty
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*only if* all messages in the ChillDKG session have been transmitted correctly over the communication links,
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and, in case of a participant blaming another participant, if the coordinator is additionally honest.
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The guarantees provided by the blame functionality are limited,
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and its primary purpose is to support manual investigation and debugging efforts.
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Different parties, even if honest, are not guaranteed to blame the same party,
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and there is, in general, no way to verify an accusation by some party that another party is to blame.
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Nevertheless, if all messages in the ChillDKG session have been transmitted correctly over the communication links,
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and, in case of a participant blaming another participant, if the coordinator is additionally honest,
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the aborting party will be guaranteed that the blamed party is indeed faulty.
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It is important to understand that this is a conditional statement.
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It is important to understand that this guarantee is conditional.
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For example, assume that the condition of a honest coordinator is violated.
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In that case, even if all participants are honest, the malicious coordinator can deviate from the protocol in a way that makes one participant blame another participant, when, in fact, it is the coordinator who is faulty and not the suspected participant.
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In that case, even if all participants are honest, the malicious coordinator can deviate from the protocol in a way that makes one participant blame another participant, when, in fact, it is the coordinator who is faulty and not the blamed participant.
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In some cases,[^incorrect-shares] an aborting participant needs to obtain an auxiliary *investigation message* from the coordinator
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before a suspected participant can be determined (see below).
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in order to single out and blame another participant (see below).
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[^incorrect-shares]: Namely, when having received incorrect secret shares.
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