Bitcoin Off-The-Grid (BOTG): secure savings script v0.1.1

[Scrat Acorns]

I hope my post isn't considered a necro but this method needs more exposure and most importantly more scrutinization (is that even a word?) by people who know the internals of bitcoin.

There should always be a secure way to create addresses offline with readily available tools in a standard linux distro. Since the privkey is generated by a single openssl command, you know 100% that it hasn't been tampered with. As opposed to trusting a website and downloading a program from it.

Am I too paranoid?

[casascius]

There's lots of ways to generate bitcoin addresses and you just need to pick the one that works best for you.  If using this script gives you the right mix of comfort and convenience, then this is the method for you.

It will be nice when generating bitcoin addresses is a feature as standard as creating a new text file or subdirectory.

[Scrat Acorns]

There's lots of ways to generate bitcoin addresses and you just need to pick the one that works best for you.  If using this script gives you the right mix of comfort and convenience, then this is the method for you.

It will be nice when generating bitcoin addresses is a feature as standard as creating a new text file or subdirectory.

I'm particularly worried by the "recreate key if hexsize != 64" deal. Won't that effectively reduce the keyspace? I know it won't be much but still.

[casascius]

There's lots of ways to generate bitcoin addresses and you just need to pick the one that works best for you.  If using this script gives you the right mix of comfort and convenience, then this is the method for you.

It will be nice when generating bitcoin addresses is a feature as standard as creating a new text file or subdirectory.

I'm particularly worried by the "recreate key if hexsize != 64" deal. Won't that effectively reduce the keyspace? I know it won't be much but still.

By about one bit.  It's an ugly hack so the script doesn't have to deal with signed numbers or leading zeros but won't reduce your security in any practical sense.

Bitcoin addresses themselves are only 160 bits, so going from 256 to 255 bits of private key is no big deal.

[salfter]

Looks like someone already necro'd this thread so I won't have to. 

I stumbled across this thread while looking for something faster than pywallet to convert hexkeys to WIF privkeys and addresses... haven't quite gotten it running yet as it appears to depend on vim, which I don't usually have installed (vim provides xxd) just got it running after installing vim. It might be worth noting in the OP that it needs vim (and openssl, but I already had that) to run.

[Red Emerald]

Looks like someone already necro'd this thread so I won't have to. 

I stumbled across this thread while looking for something faster than pywallet to convert hexkeys to WIF privkeys and addresses... haven't quite gotten it running yet as it appears to depend on vim, which I don't usually have installed (vim provides xxd) just got it running after installing vim. It might be worth noting in the OP that it needs vim (and openssl, but I already had that) to run.

Why would this depend on vim?  I don't see vim called anywhere in the script.

[grondilu]

Looks like someone already necro'd this thread so I won't have to.  

I stumbled across this thread while looking for something faster than pywallet to convert hexkeys to WIF privkeys and addresses... haven't quite gotten it running yet as it appears to depend on vim, which I don't usually have installed (vim provides xxd) just got it running after installing vim. It might be worth noting in the OP that it needs vim (and openssl, but I already had that) to run.

Why would this depend on vim?  I don't see vim called anywhere in the script.

xxd is part of the Vim package.   To avoid this dependency you can use perl as mentioned earlier in this thread.

To spare you the hassle of looking for it:

Code:

checksum() {
    perl -we "print pack 'H*', '$1'" |
    openssl dgst -sha256 -binary |
    openssl dgst -sha256 -binary |
    perl -we "print unpack 'H8', join '', <>"
}