This was due to the fact that you had installed a full node (needs to download/sync/process the whole blockchain).
Light-weight clients (electrum) do connect to a server which does provide the relevant information (balance / transactions of your addresses).





Even if you know how to protect your device, and even if you do know a lot about networks it is not guaranteed that an online wallet is safe.

The thing with online wallets is that at one point you have to rely on the web wallets server.

Imagine the following case:
Your PC is completely secured from any malware (not possible, but lets assume it).
You visit blockchain.info or any other web wallet, check whether you have entered the URL correctly (maybe use a bookmark) and verify the SSL certificate.
You then enter your credentials. A few seconds later.. everything gone.

What happened? Were you not cautious enough? No. An attacker just had a valid SSL certificate for this site issued by a CA which had a security breach.
While you were thinking you were on the online wallets server, you got directed to the attackers server (which does show a valid certificate for the online-wallets URL). You basically just got phished.
There is not a lot you could have done in this case. You might have checked whether the CA from the SSL certificate does match the previously mentioned CA and keep a list.. But that would be a really paranoid way.


Thats just one example. Online wallets do have way more attack vectors than traditional desktop-/mobile- wallets have.
You can be the most security-concerned person, but you won't never be able to keep an online wallet fully secured with no possibility of theft, ever.
 

For me, it appears after it is connected and unlocked. No application on the nano s has to be opened (at least with my setup).

@OP: It may also appear under USB-controller. Does something appear ANYWHERE when you plug in / unlock your nano s ?
Do you hear the windows sound (the sound you always here when plugging in a USB device) ?

You can export the seed from blockchain.info. AFAIK it is not possible to export single private keys (but i am not sure with this).

To export the seed, go to the 'security center' and clicking on'phrase backup'. You can do what ranochigo proposed to get your private keys. You might also import the seed into a BIP39 compatible wallet.
If you do this make sure to run https://iancoleman.io/bip39/ offline.


But regardless of the option to backup your seed, web wallets are the least-secure wallets.

If you want to be better secured, download a desktop wallet (e.g. a lightweight one which doesn't need the blockchain, https://electrum.org/#home.
Or, a better option is a hardware wallet. Unfortunately they are not that cheap. But definitely worth it if your investment can absorb the purchase.

Another way of securely storing your coins (which is not that convinient and 'easy' to spend from) is a cold wallet setup with a computer which is dedicated to store the private keys without any internet connection.

Or you can print a paper wallet to store them long term. But to spend from a paper wallet you have to import it into another wallet. Paper wallets are fine for long-term storage, but very unconvinient for regular usage.


Regardless, all of these wallet types are more secure than an online wallet.

Does a device with a yellow exclamation mark appear the moment you plug in and unlock(!) your nano s?


If yes, then remove this device from the device manager (right click -> uninstall device). The driver will be automatically installed the next time you plug it in (hopefully without any errors).

Or does a device appear which does NOT have a yellow exclamation mark? In this case the driver should be fine. May not be windows' fault in this case.

Or does nothing appear at all in your device manager when you plug it in? This may be caused by a wrong cable (power cable are not equal to data transfer cable) or a broken USB port.

honor, poor, quietly, take and ink are neither part of the BIP39 word list nor of the wordlist electrum uses.

It is really weird how electrum does generate a wallet (both, as electrum AND BIP39 wallet) with 5 words not being in the dictionary and the last word actually being 'k'. This indeed sounds like a bug.


OP, how did you find out about this? 

Coins should only be held on an exchange as long as necessary.
Practically you do NOT own these coins if you do not own the private keys. You are just given the 'right' to withdraw an amount X (data base entry).

It is advised to use a wallet where you have full control over the private keys (e.g. a lightweight client like electrum).

A cold wallet (like a ledger hardware wallet) is even better than a desktop wallet. A hardware wallet doesn't only give only you full access to the private keys, they are also isolated in an offline environment.
If you can afford a cold wallet, go for it and buy one. It is the most convenient way of securely storing your coins.

Basically thats the relative 'security ranking' of wallet types: Cold storage / Hardware wallet / Paper wallet > Desktop wallet > Mobile wallet > Online-/Web- wallet > Exchange

--reindex will wipe and rebuild the chainstate and block index.
It does not repair broken block files. You will need to resync and redownload those corrupted block files.

Did you already try to delete the latest few downloaded block files and run --reindex afterwards? It may be worth a try.
They are usually located in ~/.bitcoin/blocks/ (linux) or %APPDATA%\Bitcoin\blocks (windows).

Mostly the same.

If you are using google authenticator AND the binance application on the same device, you are not secured by a 2-factor-authentication. 2FA implies two devices.

This all depends on how much money you have on the exchange, the risk you are willing to take and your habits regarding security/safety on your mobile phone (shady applications, general permissions, ...).

Overall i would NOT risk any coins on an exchange (which by the way shouldn't be on an exchange anyway) by using it together with my GA on my mobile.

You may have to resync the blockchain.
-reindex wipes the chainstate and block index and rebuilds them.

But it seems like you have corrupt block files. The best option probably would be to sync from scratch.

Did you check wether your hardware does work as intended? Do you have the blockchain stored on an external hard drive (those are more error-prone) ?

Definitely.
The LN is still being tested currently. Once it is fully released and people start using it, there will be routing fees.
Currently it is more like testing how payments in the future will look like 




User can at any time decide to open a new channel with any person.
You do not have to open a direct channel to the person you want to pay or receive from. There just has to exist a route between you and your target (through multiple hops).

Actually, the travelling salesman problem does indeed ask for the shortest possible (=optimal) route and therefore is an NP-hard problem.

---

You seem to missunderstand the idea.
The idea is to have a PoW which can not be performed by a machine. In this case they are not vulnerable the same way. A human is not vulnerable to any kind of digital attacks/spoofing/.. the same way as a machine.

It seems you files are somehow corrupted.
Did you actually try to rebuild the database? Or did you just hit CTRL+C to cancel each time?

Probably because it is not that advised to use an exchange and handle more than a few bucks via your mobile phone.


The majority of exchanges uses googles authenticator for 2-FA.

If you login from your mobile phone which does also have the GA keys, your are basically no longer using 2-FA.
If your mobile is compromised, your whole account is compromised and an attacker can simply withdraw all your money.

Especially since also most people are logged in into their email accounts on their mobile, the attacker would have full access to the exchanges (or other) account(s).
In this case you are relying solely on your mobile phone to be secured and not compromised (which is a bad approach since it probably hasn't even the necessary security patches installed).

Yes, indeed, i never contested its correctness. Jut wanted to make the relations clear for OP or any other reader.
I did not want to create the impression that your statement is wrong. I apologize if it seemed like i did.




I fully agree.
The only realistic scenario where two user create the same keypair would be if both used a wallet with a flaw in the random number generator.
Besides that, the math behind bitcoin is definitely safe and secure.

2^256 private keys map on 2^256 public keys (1-to-1). The total amount of addresses is 2^160 (which leads to 2^96 public/private keys resulting in the same address on average).

But depending on the output type (p2pkh / p2sh) it is not sufficient to find any of the available (2^96) private-/public- keypairs to spend the UTXO's which hypothetically have been sent to this address earlier.
If the correct public key is required to redeem, you have to search through the 'full' space (2^256).

Just a small correction:
There are 2^256 possible public- (and private-) keys.
A public key is the product of a multiplication on the elliptic curve (1-to-1 mapping between private- and public key (256 bit)).


@OP: If you have security concerns, take a look at this.

What about reading the other answers?

Since you are able to build a web application, you shouldn't have any problems understanding the links mentioned by HCP:

You will be able to estimate the fee yourself after reading those articles. The implementation itself is trivial. Examples can be found on the internet.
By implementing it yourself you are independent from API service provider (which can have wrong information / downtimes and do not exist for all cryptos).

NEVER (under NO circumstances) reveal your seed or private key. ANYONE with knowledge of this seed can access and steal your coins.

Please consider those seeds as compromised. Do NOT use them anymore.
Create a new one and do NOT share it with anyone. It has to be kept private to keep your funds secure. The whole security of your coins relies on you keeping this phrase private.


For future reference:
To import a seed, downlolad a BIP39-compatible wallet (e.g. electrum) and restore your wallet from the seed.
The derivation path depends on the wallet you have used previously to access your funds (standard is: m/44'/0'/0'/)

This is definitely possible. Especially since there are pools with more than 10% hashrate each.
The majority of hashrate is being provided by Bitmain/BTC.com. You can find a graph containing pools with their hashrate here.