23
votes
How can I manually (on paper) calculate a Bitcoin public key from a private key?
I've spent a fair bit of time thinking about this and can provide a fairly comprehensive answer about the state of the art. But unfortunately the TL;DR is that we don't know how to do this (yet) in ...
- 686
18
votes
Accepted
Is it safe to reuse a Bitcoin address?
There are both security and privacy related issues that arise from address reuse. Based upon your question you are less concerned with the privacy implications and more concerned with the security ...
- 2,680
17
votes
Should I share my seed phrase to earn airdrop tokens?
No, it is not safe. Never share your 12 word phrase. It is a backup of your private key and allows people to spend your money. They only need your public key or Bitcoin address to give you money, not ...
- 422
13
votes
Accepted
Can a closed source wallet ever be completely trust-less?
The term trustless is often misunderstood. I suspect you mean not needing to trust anyone, but if a program being open source helps for that, aren't you implicitly relying on the people who are ...
- 99k
10
votes
Alert Key Compromised, upgrade required
The network wide Alert system is being retired. No Bitcoins are at risk and this warning may be safely ignored. Upgrade to the newest version of your wallet software to no longer see the alert.
Read ...
- 266
10
votes
Accepted
BIP32 recommends a 256 bit seed. Why do most Bitcoin wallets only use a 128 bit seed?
The reasons for the 3 numbers:
Bitcoin uses 256-bit ECDSA signatures. These require in the order of 2128 steps to find a private key from the public key is known. This is Bitcoin's security level: we ...
- 99k
7
votes
Is it safe to reuse a Bitcoin address?
Why address reuse is discouraged:
Reduced security An unused address is protected by ECDSA AND several SHA-256 and RIPEMD-160 operations, but only ECDSA after being used because the public key must ...
- 1,410
6
votes
Is holding funds in a Bitcoin paper wallet safe?
Yes. A paper wallet is basically nothing more than your private key on a piece of paper.
For usability it is often represented as a QR code though. You can make copies of it, and store several of ...
- 61
6
votes
Accepted
Is It Possible to Prove Ownership of Public Key Hash without Public Key?
The simple answer is no.
A hashing algorithm is ment to be a one-way function. If it is possible to recreate the public key from the hash, this means that the hashing algorithm is broken.
However ...
- 546
6
votes
Sugar Daddy Bitcoin
It is a scam.
He wants to get you comfortable with a process he can exploit later by sending you larger sums and getting you to pay an accomplice most. Maybe in a week or a month he will say he wants ...
- 24.4k
5
votes
Accepted
I'm new to Bitcoin, how do I keep my bitcoins secure?
Use a desktop or mobile wallet (Electrum or Mycelium) to spend bitcoins (be sure to write down your recovery seed and store it like a paper wallet). To receive and store them, use offline paper ...
- 291
5
votes
I'm new to Bitcoin, how do I keep my bitcoins secure?
Wallet
The wallet holds the most valuable component of the bitcoin network, your private key.
When you go to Bitcoin.org, there are several choices.
A HD wallet (Hierarchical Deterministic) is more ...
5
votes
Can a clever hacker still steal everyone's money from the blockchain.info wallet?
They anticipated this type of attack and they are monitoring their JavaScript files, check this website of theirs http://blockchain-status.com/javascript_verifier
Also, CloudFlare (the reverse proxy ...
- 51
5
votes
Would it be wise and extra secure to use non-ascii characters in a brain wallet?
It would not be wise to do this.
"Brainwallet" software is completely non-standardized, there's no guarantee that any two implementations handle the encoding of characters in the same way. Addition ...
- 15.3k
5
votes
What did I do wrong that caused me to lose bitcoin?
1) If you generate your paper wallet on your computer, you have to fully trust your computer
2) If you use a website for generating your paper wallet, a) you need to trust that website (hopefully its ...
- 5,992
5
votes
Relationship of Bitcoin address and Public Key
Addresses are textually encoded public key hashes, which means that somebody in possession of only the address cannot read the public key - but eventually the public key must be revealed in order to ...
- 3,304
5
votes
What stops a wallet from stealing bitcoins?
As @Prayank mentioned before: Nothing. As Ken Thompson said: "you can't trust code that you did not totally create yourself".
If you are paranoid, it's better that you use cold wallets and ...
- 151
5
votes
How do wallets work?
Does it create a public key based of private?
Yes, a cryptographic routine exists that computes the public key from the private key.
maybe on the wallet.dat file?
All modern wallet software ...
- 99k
5
votes
Accepted
Someon offered me btc mine trough his mining device
Yes, it's a scam. Don't send them anything.
- 2,058
4
votes
How do I restore a Multibit HD wallet from a backup using only a password?
MultiBit HD dev here.
The mbhd-*.zip.aes backup files are encrypted using an AES key derived from the wallet words. Hence you need your wallet words to do a restore from one of these.
The wallet ...
- 3,325
4
votes
Accepted
Can a clever hacker still steal everyone's money from the blockchain.info wallet?
Yes, the attack you describe is possible.
But this isn't specific to blockchain.info nor to online wallets.
If an attacker manages to run code on your machine, you're pwned.
As long as an attacker ...
- 803
4
votes
Can a closed source wallet ever be completely trust-less?
No because bitcoin wallets always have access to private keys and have the ability to communicate across the Internet. With this combination of capabilities, closed source wallets could become ...
- 2,680
4
votes
Accepted
Hardware wallet teardowns and side channel attacks
The researcher Jochen Hoenicke has done some work on the Trezor. He was able to extract the private key by monitoring the power cable with an oscilloscope.
Trezor has since updated the firmware to ...
- 71.6k
4
votes
What is the most secure operating system that I can use to store bitcoins without having to fear a hacker stealing them?
The most secure operating system is no operating system. As Pieter mentioned in the comments, dedicated hardware wallets prevent private keys from leaking out of the secure hardware enclave, and ...
- 1,011
4
votes
Accepted
Should I put my bitcoin wallet on an encrypted disk or not?
This only helps when someone malicious has physical access to you hard drive while your computer is not operational (shut down, account logged out, screen locked, etc.). When your operating system is ...
- 3,214
4
votes
Accepted
My blockchain.info wallet was hacked. How can I create a double send to foil the attacker?
So some background as to what happened here. I wanted to claim my bitcoin diamond air drop. I googled and this video came up first.
The video played this weird music which I think was hypnotic in ...
- 101
4
votes
Accepted
How does crypto exchange secure private keys?
Exchanges typically have a split storage setup. They have a hot wallet and a cold wallet. The hot wallet holds private keys on an online server that can quickly send and receive Bitcoin for when ...
- 67.3k
4
votes
Accepted
How can I safely store and trade Bitcoin and other crypto currencies?
There are several ways to store cryptocurrencies, so let's break them down by use-case and safety-level.
Exchanges
There are, broadly speaking, two types of exchanges. Centralized exchanges, such as ...
- 16.9k
4
votes
Accepted
Best OS for cold storage
Use TAILS Linux. From the website:
Tails is a live operating system that you can start on almost any computer from a USB stick or a DVD.
It aims at preserving your privacy and anonymity, and ...
- 10.1k
Only top scored, non community-wiki answers of a minimum length are eligible