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How can cyclic quorum ever come to a consensus?
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8 votes

The way the SCP protocol works, you include your quorum slices in your vote messages. So following your example, nodes would say the following: A says. "I vote to accept statement a so long as B ...

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Difference between Stellar Ledger and Blocks
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8 votes

Unlike many blockchains, such as Bitcoin with its UTXO model, in Stellar every ledger includes a logical snapshot of the complete system state. This makes it possible to trim history while still ...

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hash(x) signer in lightning network
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6 votes

A hash(x) signature has no dependence on the transaction itself. As such, it is only a "signer" in the sense that it adds signing weight to a transaction. Once anyone has seen the corresponding hash ...

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Could consensus period be changed?
4 votes

The tricky part is that the timer for the nomination rounds of the SCP protocol starts five seconds after the previous slot's nomination protocol has ended. If you want to have an arbitrary delay ...

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Does each node maintain a global ledger?
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4 votes

Yes, all nodes maintain the exact same ledger as a replicated state machine on top of the Stellar Consensus Protocol (SCP). It is a serious configuration error to have two disjoint quorums--such a ...

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How to implement OTC trading of Stellar assets?
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4 votes

Your answer is correct, except that the thing you say is impossible is actually easy. A Stellar transaction can contain up to 100 operations, and each operation can have its own source account. So ...

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Secured ways to check if a node is up working?
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4 votes

You can get the latest ledger header from horizon, for instance the following command would work from the command line: curl 'https://horizon.stellar.org/ledgers?limit=1&order=desc' Obviously ...

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What is asymptotic security and why does Stellar, but not POW exhibit this?
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4 votes

As a practical matter, SCP's asymptotic security follows from the fact that it depends only on digital signatures (and hash functions) for security, and that these can be tuned to resist arbitrarily ...

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Who creates the ballot?
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3 votes

I think you are conflating the ballot and the candidate value chosen by the ballot. The candidate value (which includes a set of transactions) is selected using a nomination protocol that typically ...

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Stellar address prefix bitwise operator rationale
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3 votes

The strkey format is a base32 encoding given by RFC4648. The first output character of the encoding is determined by the top five bits of the first byte. So the value 6 is the value corresponding to ...

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Is it possible to set up a virtual machine(like evm for smart contracts ) using stellar consensus protocol?
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3 votes

It would take quite a bit of development, but there is nothing technically impossible about this. Note that because SCP is an alternative to mining, validators won't get rewarded for executing smart ...

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Check wallet balance via API
3 votes

Just pick a horizon server to query (e.g., https://horizon.stellar.org/). Then for account balances you want the Account endpoint, which you can query like this: curl https://horizon.stellar.org/...

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Effects of a stellar-core node running on too slow hardware?
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3 votes

If the node cannot catch up, it will fall behind in the ledger state. This is a problem for anyone who uses horizon on that node. However, it would only be a problem for consensus if other nodes ...

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Nominate --> Prepare --> Commit --> Externalize question
3 votes

First, note that the values in stellar are actually sets of transactions, or actually triples with a set of transactions, a timestamp, and a list of upgrades. Second, it's a little hard to follow ...

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Why does the high level threshold level for quorum have to be above 66%?
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3 votes

This is by analogy with symmetric Byzantine agreement protocols (in which everyone has the same quorum slices). You need any two quorums to intersect at an honest node. If your threshold is 2/3 or ...

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What are the message size limitations of stellar consensus protocol?
2 votes

SCP doesn't have any theoretical limits, since really all you need to agree on is a SHA-256 hash of an arbitrary-sized set of transactions. However, the Stellar validators vote to set a maximum ...

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MultiSignature doubts
2 votes

There is no difference, practically. No, because you can consume sequence numbers at low threshold just by using the source account.

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What happens when transaction fails to be applied?
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2 votes

The rules for applying transactions are deterministic, so any validator that fails a transaction that should have succeeded is ill-behaved. SCP survives ill-behaved nodes so long as there is a well-...

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When a lower tier quorum comes to its own consensus
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2 votes

A and B cannot sync up with SCP. This is an invalid configuration. B is misconfigured, so should just dump its state and restart with better quorum slices. SCP only guarantees agreement when there ...

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How many Lumens would I have to get in order to create a custom token?
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2 votes

The issuing account doesn't actually need anything other than the normal 1 XLM, but any wallet that is going to hold your token will have to add a trust line, and doing that will increase its minimum ...

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How can I validate a Stellar address?
2 votes

The previous answer is correct, but just to be a little more precise about what is going on, Stellar private keys are computed as follows. First, a 35-byte value is computed as follow: The fist byte ...

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Questions about SCP and federated voting steps, with a focus on the Internet-Draft
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2 votes

The SCPPrepare message conveys "vote commit ballot ". However, it does not convey "accept commit c" for any c, because if it accepts any commit message then it immediately proceeds to the COMMIT ...

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SCP Safety Guarantee Question
1 votes

A node can only be befouled if there exists an ill-behaved node befouling the node. This is only true if you have nominal quorum intersection. That's why so many of the theorems say "assume an FBAS ...

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Is the Stellar Consensus Protocol paper peer reviewed?
1 votes

A peer reviewed academic paper on the Stellar system was published at SOSP in 2019. It includes a section on SCP and another section on the formal verification of SCP.

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Nomination protocol differences between implementation and specification
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1 votes

At this point, there are a bunch of small ways in which the internet draft is not wire compatible with stellar-core. The most important is that while multiple people have implemented SCP, there is ...

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Do transactions store information on when they were created?
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1 votes

The transaction can optionally contain timebounds, placing a lower and upper bound on when it may be executed. However, if you want to know whether and exactly when the transaction was executed, you ...

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How does network passphrase work?
1 votes

The NETWORK_PASSPHRASE should be made public, because it permutes how transactions are hashed. Since the passphrase determines the private key of the account containing the initial native tokens, ...

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How does the Stellar protocol ensure a network doesn't have disjoint quorums?
1 votes

Yes. Stellar Development Foundation (SDF) maintains three validators, which you can find in this list of validators. If you include at least one of them in every quorum slice, you will stay in sync ...

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SCP. Does non-intersecting quorums have different ledgers?
1 votes

1) Do all nodes in stellar-network know about my transaction and decide whether to include it in the ledger or not? Or does the decision accept only the quorum to which I belong? Yes, all nodes ...

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Is there a minimal implementation of Stellar Consensus Protocol besides stellar-core?
1 votes

I believe there are implementations either complete or in progress, but am not sure if any have been publicly released. If you want to implement SCP, I strongly recommend starting with the protocol ...

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