1

Since the private key is basically a random large number, would I be able to pick a password and have that converted into an address?

For example: pick "mysecretpwd". Have it sha256ed, obtain a large integer that is the private key from which I can easily derive the public key and the bitcoin address.

Then for spending any funds received at that address I only need to remember "mysecretpwd", no private key storage on paper, mnemonics or anything, basically the funds are stored in my brain.

What are the security/privacy implications?

4

What you are describing has been done before, and is known as a "brain wallet".

In earlier days, some wallets and online website did use this system. However, it has proven quite insecure, as humans are terrible at picking secure random data for the "password", and computers are great at guessing them. Many BTC have been stolen from insecure brainwallets, and at this point we have much better and safer means of easily accessing wallets, namely BIP39 seeds.

  • So you're saying that it is feasible for a computer to brute-force a strong 20 characters alphanumerical/symbol password that I sha256 a million rounds? – Tedy S. Sep 28 '18 at 10:00
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    @TedyS. yes. see here – Abdussamad Sep 28 '18 at 10:49
  • I think what the folks at bitcointalk were advising against is using a simple dictionary word that is susceptible to rainbow table-like attacks. I would imagine an attacker's chances drop substantially if the hashing is done multiple times, like I said earlier maybe a million. – Tedy S. Sep 28 '18 at 12:55
  • en.bitcoin.it/wiki/Brainwallet – JBaczuk Sep 28 '18 at 14:34
  • @TedyS. to be fair to Raghav, your original question did not mention a million rounds of hashing (so implicitly one only) and your example passphrase is composed only of simple dictionary words and commonplace abbreviations in all lower-case ASCII letters. Answerers can only answer the question you actually post, they can't anticipate how you might subsequently move the goalposts. – RedGrittyBrick Sep 28 '18 at 14:59

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