Why is Bitcoin such a secure technology?

[BlackJacky]

Sometimes people ask me "What makes Bitcoin so secure? Why is this technology so safe?

How would you answer this question? Do I have to answer it with regards to Proof of Work?

Thanks for your thoughts on this 

[coinsocieties]

The easiest way to explain it is that everyone has a the ability to have a copy of the Blockchain on their computer. With that said, there is no way that one person can change the blockchain everywhere in the world in order to make they changes they want to make.  The blockchain is like a chain linked dog chain.  Each link is connected to the next down the whole chain.  You can not change one of the links without the whole chain falling apart.  Each link is a math equation and there is not a way to make a change to that math equation without changing the next math equation down the chain and so on.    I know it is not the perfect answer but I hope it helps.

[LFC_Bitcoin]

The block chain is a shared public ledger on which the entire Bitcoin network relies. All confirmed transactions are included in the block chain. This way, Bitcoin wallets can calculate their spendable balance and new transactions can be verified to be spending bitcoins that are actually owned by the spender. The integrity and the chronological order of the block chain are enforced with cryptography.

Read more - https://bitcoin.org/en/how-it-works

If you want real detail check out Satoshi's original paper - https://bitcoin.org/en/bitcoin-paper

[Senor.Bla]

i bet there are many different answers to this question.
i would say, that bitcoin is this big ledger that everybody can see and check (and contribute/use), but nobody can manipulate it, one something went it.
of course you can argue that one can manipulate it. but only on the newer blocks and you would have to invest insane amounts of money to do so.

[Yakamoto]

Sometimes people ask me "What makes Bitcoin so secure? Why is this technology so safe?

How would you answer this question? Do I have to answer it with regards to Proof of Work?

Thanks for your thoughts on this 

Basically it is secure because a ton of individuals verify that the transaction happened, and said transaction cannot be reversed in any way because of this. The network collectively agrees that the thing happened, and thus it is said to have happened.

Addresses individually are secure because of the private key, which is basically way too long and complex for it to be worth most people trying to figure out what it actually is.

[Kprawn]

The network is distributed over several computers over the internet in different countries. You do not have a single target to take down, but

1000's of computers. If you want to manipulate the code, you would have to do it on all of those computers, and this is not a easy feat at

all. The software is also monitored by several developers from different countries, to see if malicious code is added, if it did happen.. people

would be notified and then nodes will not run the software.  ... The code is also public, and not proprietary like other software. 

[sugarfly]

When they ask me "can't bitcoin be shut down?" I answer "can the internet be shut down?"

NO!

A person understands bitcoin the moment she understands decentralisation.

[springgers]

Blockchain is the answer, blockchain will revolutionize the world, just wait more years.
The other point is: the banks/government don't control your wallet...

[Dalkore]

Blockchain PLUS having a ton of hardware power using profit as an incentive to verify and make sure the distributed ledger is accurate and honest.

[franky1]

bitcoin has many layers of security.

if you want a summarised version in slightly techspeak
[1]transactions: not a simple balance, but log of who pays who, containing details of last transaction
[2]encryption(keypairs): validates transactions
[3]cryptographic hashes: lock valid transactions together in blocks, where hash matches the data within the block
[4]chaining blocks(include hash of previous, in current): ensures old data cant change without being noticed
[5]longest chain: by being the longest, it shows a history of more effort put into its creation
[6]difficulty: requires result of certain 0's, more 0's more harder to achieve
[7]brute-forcing hashes(mining)(requiring result contains certain 0's): ensures a specific result hash that is harder/time consuming to get compared to a simple hash
[8]payment: motivates miners to follow the rules or their payment wont be recognised by others
[9a]distributing chains: ensures they back each other up to know the best chain available meeting same rules, disregarding the one the majority dont have
[9b]distributing chains: ensures many copies so it cant be attacked at a single location to destroy the chain


speaking to laymen i try to use words they understand, (waffly, but then explaining technicals to average people is)
a transaction it is not a total balance of one identifier, but a single instance of just one movement of who is paying who using details of the previous validated instance that an identifier had received. traceable right back to when the funds were created[1]

the first is the identity and password that validate the transaction was created by the right person by creating a message that proves only the password holder could have made it without revealing the actual password.[2]

next this data is passed around thousands of people who do the validation of that transaction message. although the next stage doesnt need it. by having thousands of people checking it, the chances the next stage receives an invalid transaction is low, allowing for fast double checking without much "spamming" happening

a block of data is formed by joining thousands of valid transactions.[3] and a hash is created that is an expression of that combined data AND the hash of the previous block of data included also. forming a chain of data blocks linked by having something from the previous block attached[4]

at this point its worth noting that changing any data, changes the hash. so anyone changing data from the past instantly ruins the chain after it, because the other hashes after no longer match.. so it takes effort to then use the new hash and then remake blocks ontop with new hashes

also worth noting that the thousands of people who eventually get this data see the longest length of valid blocks in a chain as the most trustable because it means its done the most work compared to others.[5] but this is not enough

because a hash alone is simple to produce. if someone made a chain in 2 weeks, it only takes 2 weeks for a computer double the speed to remake the same amount of blocks again. and then make more ontop to overtake the first person.

to make it hard for someone new to just make a new chain simply by having a faster computer, that hash is used to create a second hash that has a requirement of containing a number of 0's in in the second hash. thus making it a time consuming process[6]
this is done by adding a random number to keep adjusting to get a hash with certain amount of 0's in it that validates as having said first hash and the winning random number in it that got the result.

the more 0's required the more time consuming and difficult it is to get a result. the number of 0's needed is estimated to be difficult enough that it takes 2 weeks to hash 2016 blocks with these solved results. the estimate of how many 0's are needed is done by seeing if the previous 2016 blocks took less than 2 weeks. and adding an extra 0 requirement if so to add more difficulty to the task.

after a number of years it now requires the equivalent of 1,500,000,000,000 computers to get a solved result in the average timescale required.
as for the costs of doing all this. the block creator gets rewarded with coins for being the first to hand out a solution that meets all the validation rules to all the other users.[7]

to ensure those making the blocks dont do anything foolish like make their own chain of random data. the rules of what is and isnt a valid block of data and transaction is also the rules of thousands of other people. so if the data the people get is not valid, they wont accept the data and ofcourse wont accept the block creators reward. making it foolish to do soo much work for no payment.[8]

lastly because the data is now on thousands of computers, that check each other[9a] and tell each other what the current longest chain is and all agree its all valid.[9b]

its no longer a simple thing of fooling one person. but fooling thousands of people.
EG

imagine you had 10 people, where 8 of them had 20 apples each from an honest apple grower, that took a year to grow them.. if person number 9 wanted to make some new fast growing apples but only got 5, its alot harder for person 9 to convince person number 10 that 5 dodgy apples is norm if that 10th person has 8 other people saying that 10 mature full grown apples is the norm. especially if comparing the quality(hashes) of the 5th apple of the 10 mature apples doesnt look anything like the 5th dodgy apple. the 10th person will reject the dodgy apples entirely because it doesnt match what the other 8 people have.

also by 8 people having the highest amount of apples, its alot harder to kill one off to persuade person number 10 that 5 apples is valid.
imagine 6000 people with 20 apples each. the dodgy fast growing apple farmer has no chance.

and thats it.. in laymens.

[iv4n]

Nice question and topic, I also was in situation where people asked me how we know that bitcoin is safe and secure currency, and I didn't know what to tell them.
I like second comment, simple explanation and very easy to remember. Blockchain is technology for the future, people should be aware of this fact how bitcoin works and that its not easy to make a copy of bitcoin. It's good to know how to explain to someone new, I think this is perfect way, but I bet there will be more good comments here.

[shinratensei_]

When they ask me "can't bitcoin be shut down?" I answer "can the internet be shut down?"

NO!

A person understands bitcoin the moment she understands decentralisation.

the Internet can be shut down..... and the correct answer is yes... everything is always having the chance for getting a break and like the stone is very strong or harsh can be a broken and why bitcoin is can't die?

[clickerz]

Nice question and topic, I also was in situation where people asked me how we know that bitcoin is safe and secure currency, and I didn't know what to tell them.
I like second comment, simple explanation and very easy to remember. Blockchain is technology for the future, people should be aware of this fact how bitcoin works and that its not easy to make a copy of bitcoin. It's good to know how to explain to someone new, I think this is perfect way, but I bet there will be more good comments here.

Same here. Since it more technical to explain how this blockchain works and its hard to explain in laymans term. Thank you for the explanation above, bt still im trying to simplify and grasp the important details. lol

[hawkins]

because bitcoin transactions have a very difficult track with high security system, but transactions difficult to track that becomes the target of hackers upper level to always try to hack and steal bitcoin. but I guess until now bitcoin is still a safe technology

[abayan]

Nice question and topic, I also was in situation where people asked me how we know that bitcoin is safe and secure currency, and I didn't know what to tell them.
I like second comment, simple explanation and very easy to remember. Blockchain is technology for the future, people should be aware of this fact how bitcoin works and that its not easy to make a copy of bitcoin. It's good to know how to explain to someone new, I think this is perfect way, but I bet there will be more good comments here.

Same here. Since it more technical to explain how this blockchain works and its hard to explain in laymans term. Thank you for the explanation above, bt still im trying to simplify and grasp the important details. lol

I cant understand also. haha it is something more technical and the words for me are new! Though thank you for explaining . It just i cant understand the blockchain technology but now i do have some ideas or something in my mind what is all about the blockchain.

[franky1]

Nice question and topic, I also was in situation where people asked me how we know that bitcoin is safe and secure currency, and I didn't know what to tell them.
I like second comment, simple explanation and very easy to remember. Blockchain is technology for the future, people should be aware of this fact how bitcoin works and that its not easy to make a copy of bitcoin. It's good to know how to explain to someone new, I think this is perfect way, but I bet there will be more good comments here.

Same here. Since it more technical to explain how this blockchain works and its hard to explain in laymans term. Thank you for the explanation above, bt still im trying to simplify and grasp the important details. lol

I cant understand also. haha it is something more technical and the words for me are new! Though thank you for explaining . It just i cant understand the blockchain technology but now i do have some ideas or something in my mind what is all about the blockchain.

if your looking for the differences of cryptocurrency and blockchain

cryptocurrency is the umbrella term for any currency using cryptographic keypairs (public/private keys) to secure transactions or balances.
blockchain is where data is locked together in blocks that contains some info of a previous block of data to make it ever increasingly harder to manipulate old data as new blocks are formed ontop.

some blockchains dont need to be public.
some blockchains dont need to be transacting in logs of fund movements, but instead total balances group agrees
some blockchains dont need to contain data related to financial value

but as long as there is a block of data, chained to other blocks of data. its a blockchain

which is why banks and other corporations outside bitcoin are missing the whole concept. by only colourfully talking about 1 security feature which on its own is not strong. they will never get something as immutable as bitcoin

bitcoin works great because it uses both cryptocurrency tech, blockchain tech and atleast 8 other security features aswell.

[davis196]

Sometimes people ask me "What makes Bitcoin so secure? Why is this technology so safe?

How would you answer this question? Do I have to answer it with regards to Proof of Work?

Thanks for your thoughts on this 

To be honest,i don`t know.I`m not such a nerd.

There is no 100% secure technology ,but bitcoin is secure enough.

I think that bitcoin is more secure,compared to all the other altcoins.

[Viyamore]

Sometimes people ask me "What makes Bitcoin so secure? Why is this technology so safe?

How would you answer this question? Do I have to answer it with regards to Proof of Work?

Thanks for your thoughts on this 

In my own words and opinion blockchain makes bitcoins secured.
A blockchain which transaction and confirmations is the path of which makes it secure the proof is what you will only see is the transaction numbers ,you can't see the real identity of sender or receiver and even the hackers can't trace it .

[passwordnow]

Because bitcoin has a good developers and think about the risk and focus more to the security of it. And for sure no one is going to ever break down the security of bitcoin and as well as the blockchain technology that is being used by a lot of bitcoin people. This is one of the strongest and secured currency in the world.

[AGD]

Nice question and topic, I also was in situation where people asked me how we know that bitcoin is safe and secure currency, and I didn't know what to tell them.
I like second comment, simple explanation and very easy to remember. Blockchain is technology for the future, people should be aware of this fact how bitcoin works and that its not easy to make a copy of bitcoin. It's good to know how to explain to someone new, I think this is perfect way, but I bet there will be more good comments here.

Same here. Since it more technical to explain how this blockchain works and its hard to explain in laymans term. Thank you for the explanation above, bt still im trying to simplify and grasp the important details. lol

I cant understand also. haha it is something more technical and the words for me are new! Though thank you for explaining . It just i cant understand the blockchain technology but now i do have some ideas or something in my mind what is all about the blockchain.

if your looking for the differences of cryptocurrency and blockchain

cryptocurrency is the umbrella term for any currency using cryptographic keypairs (public/private keys) to secure transactions or balances.
blockchain is where data is locked together in blocks that contains some info of a previous block of data to make it ever increasingly harder to manipulate old data as new blocks are formed ontop.

some blockchains dont need to be public.
some blockchains dont need to be transacting in logs of fund movements, but instead total balances group agrees
some blockchains dont need to contain data related to financial value

but as long as there is a block of data, chained to other blocks of data. its a blockchain

which is why banks and other corporations outside bitcoin are missing the whole concept. by only colourfully talking about 1 security feature which on its own is not strong. they will never get something as immutable as bitcoin

bitcoin works great because it uses both cryptocurrency tech, blockchain tech and atleast 8 other security features aswell.

Pretty much offtopic, but it's a lot of fun to watch even the best worldwide financial market analysts failing to understand the Bitcoin concept.