Incoming debit transactions in statements

I have a question. In my bank statement there are few incoming transactions such as 800 or 1000 or 2500 apart from my monthly salary. Actually these amounts are mine which my friends paid back to me as i have paid for various reasons such as we were traveling together or outing and having dinner together and the expenses occurred is paid by me thru credit card and sharing charges are paid back to me from their back account online. How can i justify this scenario to visa officers while submitting the application for UK visit visa. Kindly advise.

Thanks in advance.

How can I calculate/estimate how quickly a machine can verify transactions on the blockchain?

If I have some machine with particular specs in mind (processor/memory/bandwidth), how can I estimate how quickly that node can download and verify transactions? In a quick search I wasn’t able to find any numbers for verification speeds run on different machines, so that would be helpful too.

I have seen this question, but my question is more focused.


I found one bit of data about this: a lower bound of verification of last year’s blockchain in about 20 days (projected, not tested). This amounts to about 170 transactions per second of verification.

No transactions are showing on my Blockchain page

I’m new to this but I know how to use the request button on BlockChain to receive money? The Bitcoin was sent to the address I provided and I didn’t get it. I’ve received money before and sent money and none of this is showing. Transactions aren’t even showing on my blockchain home page. I’ve always used the same email address. There is always change in my Blockchain account and that not there is either. I done this over may 7times probably and never had an issue. Was I hacked? The day I requested the money I thought it was odd that no change was in there because there is always 95 cent to 50 cents in the blockchain. Because the money was sent 10 days ago. The company sent me all the information and I’ve never had any issue before with blockchain. Can somebody help? NO TRANSACTIONS are showing up in my whole time using blockchain and I find that odd.

Do Full Nodes validate all transactions and make new blocks after all bitcoin are mined?

Do Full Nodes validate all transactions after all bitcoin are mined?

A fork of bitcoin core with all coins pre mined would be behaving in this way too I’d imagine..?

Also, would these nodes still create blocks of transactions, if so, why dont full nodes do this now? Is mining only a safety mechanism for a permissionless network?

See this quote at the link below:

Blockchain Validation vs Blockchain Consensus

It’s important to note that “validation” and “consensus” aren’t the same thing. A Blockchain Validator performs validation by verifying that transactions are legal (not malicious, double spends etc).

However, Consensus involves determining the ordering of events in the blockchain — and coming to agreement on that order.

Essentially, Consensus involves agreeing on the ordering of validated transactions.

The validation precedes the Consensus. We may very well have something that is “valid” that the network does not “agree” upon.

Grouping sales transactions by person

I have a csv file with sales transactions. Each transaction includes person identifiers (which are sometimes/often missing) and transaction data. Person identifiers are fname, lname, phone, email and social security number. I want to link each transaction to a unique person. As a business rule, I have set that two transactions belong to the same person if fname and lname are identical AND at least one of the 3 other person identifiers are identical. As an outcome, I need to have two dataframes (and ultimately two csv files): one with the unique persons and one copy of the initial data with an additional column for the person id.

I have written code that works very well for solving the problem for small files. Except that when the file gets really long (hundreds of thousands of lines), it gets stuck. I am almost sure that my code is not optimized and I think I can find a better way using agreggate functions like groupby() or unique(), which I think are much faster. But I can’t figure out how.

import pandas as pd workDir=r"D:\fichiers\perso\perso\python\unicity\"   sourceFile='rawdata.csv' inFrame=pd.read_csv(workDir+sourceFile, sep=";",encoding='ISO-8859-1') personFrame=pd.DataFrame(columns=('id','fname','lname','email', 'phone','social security number')) outFrame=pd.DataFrame(columns=inFrame.columns) idPerson=0 #print(inFrame)   def samePerson(p1, p2):   response=0   if p1['fname']==p2['fname'] and p1['lname']==p2['lname']:       if p1['email']==p2['email'] or p1['phone']==p2['phone'] or p1['social security number']==p2['social security number']:         response=1   return(response)  def completePerson(old, new):     #complete with new line missing data in ols version of the person     for theColumn in ('fname','lname','email', 'phone','social security number'):         if pd.isnull(old[theColumn]) :             old [theColumn]=new[theColumn]     return(old)  def processLine(theLine):   global personFrame   global idPerson   global outFrame   theFlag=0   for indexPerson, thePerson in personFrame.iterrows():        if theFlag==0:           if samePerson(theLine,thePerson):               theLine['idPerson']=thePerson.idPerson               personFrame.loc[indexPerson]=completePerson(thePerson, theLine)               theFlag=1   if theFlag==0:       theLine['idPerson']=idPerson       idPerson=idPerson+1       personFrame=personFrame.append(theLine)   outFrame=outFrame.append(theLine)   def processdf():     inFrame.apply(processLine, axis=1)     with open(workDir+'persons.csv','w', encoding='ISO-8859-1') as f:         personFrame.to_csv(f, index='false')     with open(workDir+'transactionss.csv','w', encoding='ISO-8859-1') as f:         outFrame.to_csv(f, index='false')  processdf() 

Understanding private keys, public keys, adresses and transactions

I need some claryfication about the things, here it goes: 1. For what I’ve read, for generate a bitcoin address is following this flow:(General speaking) Private Key (SK) -> Public Key (PK) -> Address (A). Some say that SK -> PK == A. Which one is correct? 2. Now, in a transaction when X to Y of “n” bitcoins happens this: X signs (digitally) the transaction “t” with its SK and this the part that I don’t get it. How “Y” does to open and verify that the transaction was send from X? or besides that X signs the transaction he encrypts? the transaction again with the PK/A of Y for Y can open it? There’s something that I missing?

Note that my native language it’s not english and it’s hard for me to understand this complex topic.

Thanks in advance

How does Blockstream’s Liquid Bitcoin network work to make fast bitcoin transactions?

Blockstream’s Liquid network can facilitate instant bitcoin transactions on their network. How does it work exactly?

My main questions are:

As a user with BTC on some exchange that supports Liquid Bitcoin (LBTC).

  • Is Blockstream Liquid like an exchange for exchanges that only exchanges use?
  • How is the 10 min blocktime eliminated?
  • Can regular users be on the Liquid Network and with what wallet?
  • What is their roadmap if any?

How does the Stellar protocol validate transactions?

From the dev docs:

“Once stellar-core receives a transaction, either given to it by a user or another stellar-core, it does preliminary checks to see if the transaction is valid. Among other checks, it makes sure that the transaction is correctly formed and the source account has enough to cover the transaction fee.

Stellar-core doesn’t check things that require inspecting the state of the ledger beyond looking up the source account—e.g., that the destination account to which the transaction is trying to send exists, that the account has enough of this asset to sell, that it’s a valid path.”

So who checks that these aspects are legitimate? How does Stellar protocol prevent overspend attempts?