salfter
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November 12, 2012, 10:31:55 PM Last edit: November 12, 2012, 10:45:05 PM by salfter |
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Another possibly useful bit of code that creates QR codes in SVG format: This depends on netpbm and qrencode. Basically, what we do is create a QR code PNG, convert it to a PBM text file, and mangle that with an awk script (an admittedly naive script, but it should work for addresses and private keys) into an SVG file. First, the awk script, which we will call pbmtosvg.awk: #!/usr/bin/awk -f BEGIN {getline; getline; w=$1; h=$2; y=0; print "<svg xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\" width=\""w*3"\" height=\""h*3"\">"} {for (x=0; x<w; x++) if (substr($0, x+1, 1)=="1") printf("<rect width=\"3\" height=\"3\" x=\"%i\" y=\"%i\" />",x*3,y*3); else printf("<rect width=\"3\" height=\"3\" x=\"%i\" y=\"%i\" style=\"fill:#FFFFFF\" />",x*3,y*3); y++} END {print "</svg>"}
It reads the dimensions out of a PBM text file, then writes a grid of black and white rectangles into an SVG file. To use it, try something like this: for i in 1JzFx4iQqnpyBaQbjfZ9Tg2u4KzkSpTDzi 5HzQEdP55SGjBawGCw25A14FcjegFyPtbn3xhzb1rhpxX5dZcc4; do qrencode -s 1 -l M -o - $i | pngtopnm | pnmnoraw | ./pbmtosvg.awk >$i.svg; done
Some examples: 1JzFx4iQqnpyBaQbjfZ9Tg2u4KzkSpTDzi 5HzQEdP55SGjBawGCw25A14FcjegFyPtbn3xhzb1rhpxX5dZcc4 You can then merge these with one of the SVG note designs already given however you want. I'm thinking a little HTML file with some CSS positioning info should work to overlay QR codes (and, optionally, text) over a note. By keeping all images in SVG format, your notes should print at whatever resolution your printer can deliver.
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The Bitcoin network protocol was designed to be extremely flexible. It can be used to create timed transactions, escrow transactions, multi-signature transactions, etc. The current features of the client only hint at what will be possible in the future.
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casascius (OP)
Mike Caldwell
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The Casascius 1oz 10BTC Silver Round (w/ Gold B)
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November 12, 2012, 10:34:27 PM |
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Next time I revisit this image, it needs to have some color bleeds so that minor variations in cutting don't result in white stripes along the edges.
If someone else beats me to it, please add bleeds.
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Companies claiming they got hacked and lost your coins sounds like fraud so perfect it could be called fashionable. I never believe them. If I ever experience the misfortune of a real intrusion, I declare I have been honest about the way I have managed the keys in Casascius Coins. I maintain no ability to recover or reproduce the keys, not even under limitless duress or total intrusion. Remember that trusting strangers with your coins without any recourse is, as a matter of principle, not a best practice. Don't keep coins online. Use paper or hardware wallets instead.
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salfter
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November 13, 2012, 11:23:18 PM |
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I've put together an offline note generator: https://github.com/salfter/btcnotes/Notes are rendered four to a page. Five denominations (0.5,1, 2, 5, and 10 BTC) are currently supported, each of which prints in its own color. Addresses and private keys are generated on-the-fly, rendered as both text and QR codes. Page layout is done in PostScript with artwork that started out as SVG, so you get the highest print quality possible. For convenience, final output is to PDF. I considered using HTML and CSS to position SVG images directly, but print quality proved a bit hit-or-miss...Firefox was usually OK, but Chrome frequently rendered SVG elements at 72 dpi or so before printing. Even with Firefox, I sometimes had some unexplained print failures. For sample output, try this: https://dl.dropbox.com/u/57535575/job2948.pdf
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teflone
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November 13, 2012, 11:35:51 PM |
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point me to a link that generates those with a unique private key... (wallet)
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Mushroomized
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Hello!
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November 14, 2012, 01:10:36 AM |
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I've put together an offline note generator: https://github.com/salfter/btcnotes/Notes are rendered four to a page. Five denominations (0.5,1, 2, 5, and 10 BTC) are currently supported, each of which prints in its own color. Addresses and private keys are generated on-the-fly, rendered as both text and QR codes. Page layout is done in PostScript with artwork that started out as SVG, so you get the highest print quality possible. For convenience, final output is to PDF. I considered using HTML and CSS to position SVG images directly, but print quality proved a bit hit-or-miss...Firefox was usually OK, but Chrome frequently rendered SVG elements at 72 dpi or so before printing. Even with Firefox, I sometimes had some unexplained print failures. For sample output, try this: https://dl.dropbox.com/u/57535575/job2948.pdfI think the notes should go from 1-256, each .01 raising the hue level a bit, that way it will give a cool effect,
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hi
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salfter
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November 14, 2012, 01:26:42 AM |
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I think the notes should go from 1-256, each .01 raising the hue level a bit, that way it will give a cool effect, I was aiming for standard denominations that mirror existing paper currency. (At present value, I should probably do 0.1 and 0.2 BTC notes as well.)
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Mushroomized
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Hello!
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November 14, 2012, 01:45:21 AM |
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I think the notes should go from 1-256, each .01 raising the hue level a bit, that way it will give a cool effect, I was aiming for standard denominations that mirror existing paper currency. (At present value, I should probably do 0.1 and 0.2 BTC notes as well.) But 1-256 is computery
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hi
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salfter
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November 14, 2012, 06:09:18 AM |
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point me to a link that generates those with a unique private key... (wallet)
If you're referring to my project, you need to clone it from the GitHub repo, make sure you have the software (including vanitygen) listed under Prerequisites in the README, and run the script. Each run generates new privkeys for each note. It's intended for offline use; it's not offered as a web service. If you're referring to something else, never mind.
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Mushroomized
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Hello!
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November 15, 2012, 07:55:55 PM |
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I wanted something extremely simple & something that is cheap to print. So that they can use these in Africa
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hi
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Mjbmonetarymetals
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November 16, 2012, 01:20:04 AM |
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Bitrated user: Mick.
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salfter
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November 19, 2012, 08:11:32 PM |
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I've updated my generator: https://github.com/salfter/btcnotes/It now produces 3/4" squares with human-readable privkeys that can be placed over the privkey QR codes before applying your tamper-evident labels. Black boxes are also generated on the back opposite the privkey QR codes; if nothing else, they'll help you line up the label on the back. Here's an example of the output of this version: https://dl.dropbox.com/u/57535575/job5456.pdf
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dserrano5
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November 20, 2012, 09:02:09 PM |
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What do you mean "Printer manufacturers are controlled by reptilians"? Is it actually insecure to print something sensitive, then connect the printer to an internet-connected machine? Even when power cycling it?
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Elxiliath
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December 01, 2012, 04:16:30 AM |
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Wow, this application is awesome!!! I tried to do something like this myself, but it wasn't so easy. Thanks so much for this Cas!
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Mushroomized
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Hello!
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December 01, 2012, 08:05:55 PM |
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So do you guys have any ideas how to use these for offline storage? I mean aside from genning the keys offline, printing them and storing them, do you guys do anything else to be super safe
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hi
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casascius (OP)
Mike Caldwell
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The Casascius 1oz 10BTC Silver Round (w/ Gold B)
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December 01, 2012, 08:33:22 PM |
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My alpha version (source on github, binary+source at https://casascius.com/btcaddress-alpha.zip ) allows the creation of two-factor passphrase-protected notes. If one computer is used to hash the passphrase, and you transfer the hashed version of it to another computer to produce the notes (via the "intermediate generator"), it would require a compromise of both machines for anyone to be able to decrypt the notes.
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Companies claiming they got hacked and lost your coins sounds like fraud so perfect it could be called fashionable. I never believe them. If I ever experience the misfortune of a real intrusion, I declare I have been honest about the way I have managed the keys in Casascius Coins. I maintain no ability to recover or reproduce the keys, not even under limitless duress or total intrusion. Remember that trusting strangers with your coins without any recourse is, as a matter of principle, not a best practice. Don't keep coins online. Use paper or hardware wallets instead.
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fivemileshigh
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December 02, 2012, 10:42:10 AM |
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Is there a mac version of the note-printer utility? thanks!
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casascius (OP)
Mike Caldwell
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Activity: 1386
Merit: 1136
The Casascius 1oz 10BTC Silver Round (w/ Gold B)
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December 02, 2012, 01:06:41 PM |
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Is there a mac version of the note-printer utility? thanks!
There's a web version available at bitaddress.org. My understanding is it can be compiled for Mono (probably only if you're into compiling stuff yourself, this won't be point-and-click). And it certainly runs under Windows using Parallels, Bootcamp, or any solution allowing Windows itself to run on a Mac.
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Companies claiming they got hacked and lost your coins sounds like fraud so perfect it could be called fashionable. I never believe them. If I ever experience the misfortune of a real intrusion, I declare I have been honest about the way I have managed the keys in Casascius Coins. I maintain no ability to recover or reproduce the keys, not even under limitless duress or total intrusion. Remember that trusting strangers with your coins without any recourse is, as a matter of principle, not a best practice. Don't keep coins online. Use paper or hardware wallets instead.
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