Edit: We have a great blog post about this on our blog, but I also answered below.  Check out the blog for more info: https://hackernoon.com/how-to-get-paid-for-open-source-6e13bb238a7f

Great questions!

Dual Licensing is where a project is developed under one main license, but also sells the ability to license the code using an alternative license.

This usually plays out where an open source project is developed using the GNU General Public License (aka the GPL).  The GPL is a "copyleft" or "viral" license, which means that all other projects that utilize or depend on that open source project must also be released under the GPL.  The GPL also stipulates that the source code for all components of a project must be available.  This is really cool for project creators, because they can put their work out into the world for anyone to use for free with the condition that if anyone builds upon it, they must also contribute those changes back to the community by releasing the source of their software.  For example, the most famous open source project, Linux, is licensed under the GPL, and this has facilitated collaboration that has culminated in Linux powering most servers and mobile phones on earth.

This means that, for example, Microsoft can't use any code released under the GPL in Windows because they would have to release Windows under the GPL and make all the source code for Windows available, which they don't want to do.  For this reason, many companies forbid the use of GPL licensed components in their own software, because they wish to keep their source closed.

This is where dual licensing comes in.  Even though your code is primarily released under the GPL, you can sell a proprietary license that does not have the copyleft / viral restrictions of the GPL and does not require the buyer to release their own code under the GPL, so the buyer can keep their source closed.  This is also called "selling an exception to the GPL" and you can read some of Richard Stallman's (creator of the GPL) writing on this topic here: https://www.fsf.org/blogs/rms/selling-exceptions

Our system lets you sell that proprietary license on the blockchain for ETH.  So now, anyone can get paid for their code just by listing their project for sale in our smart contract.  The license sale is logged immutably to the ethereum blockchain so you can always prove that you bought a legit license.

Thanks!

P.S. I am Chris Cassano, co-founder of Deco.Network and I'll be here from time to time, but cryptoreadyplay is also helping Deco.Network with community relations, and is an official representative for us here.

We have a version deployed on the Ropsten testnet right now, and are hoping to move it to the mainnet soon.  We are in the middle of the audit process right now.  Check it out here: https://app.deco.network/



Sign up for the alpha test here: https://app.deco.network/ and we will be airdropping tokens to early testers when the token is released.  We are firm believers that the early users and testers of our system should be rewarded. 

Your feedback is valued, and we want to build something that people want to use and will like, so please tell us your thoughts if you give it a try.  Good feedback and positive contributions to the project will also be rewarded.

Piper Wallet / Cryptographi.com Affiliate Program

Sign up here: https://cryptographi.refersion.com


What is Piper Wallet / Cryptographi?
Piper Wallet is a device used to store Cryptocurrency securely.  Piper provides the end user with the ability to create a paper wallet by pressing one button.  Piper also has more advanced features, and since Piper is based on the Raspberry Pi, Piper is actually a full computer with USB ports and an HDMI port. Piper Wallet is manufactured by Cryptographi.
 
What is the Cryptographi Affiliate Program?
The Cryptographi Affiliate Program allows you to earn 8% from every product purchased on Cryptographi.com through your referral link. Referral commission does not include tax or shipping and at current prices is $18.32 per Piper.

How do I join the Cryptographi Affiliate Program?
You can sign up for the program at this link: https://cryptographi.refersion.com

What if I want to take this to the next level?
Let’s talk! We’re interested in opportunities and expanding Cryptocurrency around the globe. Possibilities include batch file uploads and API access.  Email chris@cryptographi.com for more info.

I definitely agree, and I think you have a great attitude about this.



So there are a lot of random mods that I've done to Raspbian to get Piper to perform as best as possible.  I always figured people would just start from the SD image instead of starting from scratch.  I'll try and document the process to get everything running from a fresh raspbian install.


Did you pick it up recently?  I haven't been able to find Model A's for $25 for a few months now, it's been sold out at all the official RPi distributors. I think they were going to do a new production run of them soon so maybe that happened?




I definitely agree with this :-D

Hi, I'm the creator of Piper Wallet, now part of Cryptographi, Inc (http://cryptographi.com).  I'm glad to see other people working in this space!

I just want to point out that Piper Wallet is and has always been open source (GPLv3), and we've encouraged users to build their own units from day 1 in July 2013. 

We provide the source on our github: https://github.com/piperwallet/Piper
And we also provide full SD card images, so if you already have an SD card and an RPi you don't need to buy anything: http://piperwallet.com/sdimages/

I also want to point out that the OP is being a bit disingenuous when he claims that you can build a "PaperBank" for $60, because he's leaving out critical components that are required to even turn the RPi on.

• Raspberry Pi Model B - $35
• USB thermal printer from aliexpress (linked by OP): $37
• High quality SD card that isn't prone to corruption - $12
• 2a USB Power supply (linked by user 'imnotzorg' above) - $6
• Thermal paper for your printer (cheapest I could find on amazon, 10 rolls) - $10

Those items are required just to get the Raspberry Pi running and printing.  Not to mention that all those items come from separate online stores and all have associated shipping costs.  Assume it costs $10 total to ship all the items listed above and you're already at $110. 

I'm excited to see other people working on paper wallets, but it's a bit disappointing that OP didn't do a bit more searching when starting the project.  Piper supports all the features OP is working on (and a lot more!) so it would have been great to put that development effort into something that hasn't already been done. 

Piper will back your keys up to a flash drive if you wish.  So I keep my keys on paper and on a handful of flash drives distributed geographically around the world.  You can also use your own USB laser or inkjet printer.


You can do it either way.  You can buy your own Raspberry Pi, which we sell preloaded with the Piper software here: http://cryptographi.com/products/raspberry-pi-w-piper-software-preinstalled

Or, you can just buy the Piper SD card which also comes preloaded with the Piper software (you'll need your own Raspberry Pi) here: http://cryptographi.com/products/piper-sd-card

Or, you can buy your own SD card and Raspberry Pi and flash it with our software image, which you can find here: http://piperwallet.com/sdimages/

In case anyone's wondering what the deal is with Cryptographi.com, it's the new company behind Piper.  We've just launched the new web store for Piper on Cryptographi.com so that is where you can now place your orders for Piper.

Thanks everyone!

You can find updates, SD card images, and more at the Piper subreddit located here: http://www.reddit.com/r/piperwallet

Note: I have not released an update zip file for the latest software version (v1.06) yet, but I have released the SD card image.  So that means to update the software right now, you have to image your SD card with a computer.  I will be releasing an update zip file that you can put on a flash drive and stick into Piper to do the update without disassembling your Piper soon.

Thanks everyone!

Hey Everyone,

If you haven't heard of Piper, check it out here: https://piperwallet.com.  Piper is a self contained hardware paper wallet printer, but it does more than just print wallets because it's powered by a Raspberry Pi which is a full computer.

We've sold over 300 units since we started making Piper last year.  We couldn't have done it without the support of the bitcoin community so thank you everyone!

I just wanted to let everyone know that we've recently added Dogecoin, Feathercoin, and a whole bunch more alt coins (full list is on the FAQ on our website) to latest software release (v1.06).  You can switch which coin Piper prints by plugging in a mouse and display and going to the Settings tab of the Piper application. 

We've also added Shamir's Secret Sharing Scheme, we made printing faster, and we added the ability to paste in any text and print it with the internal printer both as plain text or encoded as a QR code. 

Finally, we updated the copies of bitaddress.org and liteaddress.org and we added dogeaddress.com to the Piper software release. 

Thanks so much everyone for your support!

Well of course, the whole point of SHA2 and other cryptographic hash functions is that they are designed to have very strong uniformity guarantees. 

Just one minor nitpick.  We're not testing the hardware RNG directly, we're testing the final output of /dev/random when it's being continuously fed entropy from the hardware RNG.  /dev/random has it's own whitening algorithms and doesn't JUST use the entropy provided from the hwrng, it pulls from a number of other places as well. 

I agree with you that using JUST the output from the hwrng is unsafe.  So that's why we feed the entropy into /dev/random and don't use it directly.  Our test is testing the system as a whole.

Your points are certainly valid though.

Oh good point, I overlooked that detail.  I understand your thoughts on this and fully agree.

I totally understand and I agree with the need for your script.  I just want to point out that I have indeed tested /dev/random being fed by the HRNG on Piper with all 26 of the "good" dieharder tests of randomness and it passed all of them.  So at least we can be confident that the randomness is statistically sound and we're not just blindly trusting it.



This makes perfect sense and having the ability to still generate secure keys on a device with a broken rng is an insanely cool idea.  


Wow, it sounds like you put a lot of effort into making sure this is a rock solid implementation.  Thank you for taking the time to do this!


The way the code on Piper is written (all python btw), you could easily hack it to support morse code on it until the user does something like holds the button down for 10 seconds to indicate that they are satisfied.  Piper does also have a bunch of spare GPIO pins so you could also add your own button(s), or repurpose the remember/forget switch to be used for the morse code input.  That would require a bit of soldering though.  

Finally, don't forget that Piper is running a full linux distro and also has an HDMI port and a USB port so a user could hook up a keyboard and use your unmodified script if they like.  I'm thinking about putting a button in the Piper GUI that essentially just launches your script, because combining all those forms of entropy with the whitening and everything is a really cool idea.


Edit: After looking over your code some more, it's clear that you put a ton of effort into this.  I donated ~$10 in BTC to your forum address to say thank you.

Unauditable?  Check this tool out: http://www.phy.duke.edu/~rgb/General/dieharder.php

The RNG in Piper has passed all 26 tests in that program that have a rating of "good".  The "good" thing is because the developer also includes tests that are questionable, so we only tested Piper on the ones he rates as "good".  Here are the results: http://piperwallet.com/dieharder-results.txt

So the RNG in Piper has in fact been statistically audited for secure randomness and passed all tests to prove it.  I store my own coins in Piper and I wouldn't feel safe accepting anything less than that.

This problem is what I created Piper to solve.  Piper is a permanently offline hardware paper wallet generator and printer and so much more powered by the Raspberry Pi platform.  It gets it's randomness from a hardware random number generator that uses thermal gradients to produce entropy. 

How do you know it safe though?  It uses community-accepted methods to do the key generation, and it's open source, so you can easily check the code yourself and make sure it's not doing anything sketchy.  All Piper software is written in python so the source is included, and it's not a lot of python so I believe most programmers could fully audit the code in a short period of time.  The only non-python part of the key generation is vanitygen.  But the source for vanitygen is included, and you can easily build it by typing "make' and then compare the binary you just built to the one used by Piper by doing an MD5 hash on both.  You can also compare the code on Piper to the code in the vanitygen github repo to make sure there is no foul play there as well. 

So if you want a turnkey solution to this problem, check out https://piperwallet.com

Hi deepceleron,

I’m the guy behind Piper.  This is a cool alternative to standard entropy collection, however, Piper uses a hardware random number generator which collects entropy from thermal gradients.  It does use a vanitygen binary, but that's because it supports setting your own address prefix and generating vanity keys.  But, the source for vanitygen is included and you can easily compile it yourself and compare the MD5 of the binary to the one used by the Piper software. 

RNGD runs on Piper and continuously feeds entropy into the /dev/random entropy pool from the hardware random number generator.  Vanitygen is called with parameters to tell it to use /dev/random instead of the default which is /dev/urandom.  Vanitygen is widely accepted in the bitcoin community as a good tool to generate safe keypairs and is used by hundreds of people everyday. 

So my point is, that the key generation method used by Piper is perfectly safe and the same solution widely used in the bitcoin community everyday.  I put a lot of thought into it and took community advice into account to make sure that the solution Piper uses is secure and safe.  I store my own coins with an unmodified Piper and I feel totally safe doing so.

That said, this is a really cool alternative to the standard entropy collection methods and if some community members can do a code audit on it and give it a thumbs up, I'm happy to include it on the base Piper SD card image or even eventually integrate it with the Piper GUI software.  I love giving people options, and this is a really cool one, especially for people who mistrust the OS random number generator.

Finally, I know you mentioned adding BIP0038 to this script.  Here's a python implementation of BIP0038 which should get you quite a bit closer to that goal.  I believe it could be added to your single file since it's only about 40 lines: https://github.com/zimage/python-bitcoinlib/blob/e9506aba6d53ad5bf760d67815d711a1c55b2557/bitcoin/bip38.py

That BIP0038 implementation has also been looked over by jgzarik in a pull request for the python-bitcoinlib and he doesn't seem to have any issues with it: https://github.com/jgarzik/python-bitcoinlib/pull/5

Thanks for making this really cool script.  I love creative ways of generating entropy!

Actually, this is one of the big draws of the service.  Since sending snail-mail is so rare nowadays, a postcard is almost like an of out-of-band method of communication.  Nobody expects to get a postcard in the mail from someone they know, so it's quite a nice surprise when one does show up. 

Huh, where do you live that this happens?  In CT, my mail is not bundled at all, so I glance at each item before I throw it away.  Also I would think that the bundled items would be shipped bulk-mail rate, but these cards are shipped standard first class postage so shouldn't be bundled in with the junk.  These postcards should be just like if you were on vacation and threw a stamp on a postcard you bought in a gift shop.

Thanks for the heads up though!

Sorry about that, I fixed that in the FAQ as well.  We do in fact allow international ordering now

You're getting an invalid file error because it's JPG only and you're probably uploading a PNG or something other than JPG.  I just changed it to accept PNGs as well, so hopefully it should work for you now.  Sorry about that!



Thanks for the heads up, I forgot that I had that info on the FAQ page.

Check your mail for a code for a free card

Haha whoops, that's quite an error.  Thanks for catching that!