Background on the mechanics of the ether pre-sale

Throughout the run-up to the ether sale we might be releasing a collection of weblog posts concerning our improvement plans and meant organizational construction. At the moment we describe a number of the background particulars of the ether sale module.  The sale module might be displayed on our web site at https://www.ethereum.org at some stage in the sale.

What’s it?

The ether sale is an HTML/JavaScript internet utility that allows individuals and organizations to pre-purchase ether tokens with bitcoin. Ether could also be bought by events keen on utilizing it of their improvement of distributed functions on the Ethereum platform or just to pay for using functions on the platform as soon as the genesis block is launched.  The applying runs largely contained in the browser, together with pseudo random quantity era (PRNG) and encryption/decryption of person secrets and techniques.

Moreover, we might be making out there a standalone pure Python utility that can be utilized from a command line interface to buy ether in lieu of utilizing the web site retailer.

Web site workflow:

1. After agreeing to the shop’s Phrases and Circumstances, the client enters the specified quantity of ether to buy, their e mail deal with, a password to make use of for encryption, and generates a “random” seed forming the premise for his or her transaction-specific bitcoin & Ethereum addresses.
2. The person purchaser sends cost in bitcoin to the generated deal with which is displayed on the shop web page and in addition supplied in a downloadable encrypted pockets file. When the browser, which is monitoring the bitcoin blockchain, sees sufficient funds have been despatched to this generated deal with, the browser creates a brand new transaction forwarding the bitcoin to the genesis sale deal with. This transaction is signed by the client’s browser and submitted to the bitcoin community. No transaction knowledge is saved on the any servers as a result of the Bitcoin blockchain serves as the acquisition database.
3. After the transaction has been efficiently submitted, the person purchaser is once more prompted to obtain a backup copy of their encrypted pockets along with being emailed one other backup file.  The customer must be conscious that holding the pockets as an e mail attachment in an e mail account for any time frame represents a vulnerability.  The e-mail attachment must be downloaded to a secure pc on the earliest alternative and the e-mail must be expunged from the e-mail system.

(What follows is technical data, the GUI we’ve got developed abstracts all of that is in a really user-friendly method)

Pockets encryption course of: 

1. Randomgen a SEED.
2. BKPKEY = sha3(SEED + “x02″)[:16]
3. KEY = pbkdf2(PW)
4. ENCSEED = encrypt(KEY, SEED)
5. WALLET = [ ENCSEED, BKPKEY ] (plus non-sensitive knowledge like ethereum and bitcoin deal with)

The BTC and ETH privkeys and addresses are derived from the SEED.

Seed restoration course of: 

1. WALLET + PW restoration:  (regular)
2. KEY = pbkdf2(PW)
3. SEED = decrypt(KEY, ENCSEED)

Overview of web site steps for making an ether buy:

1. Purchaser clicks “Purchase Ether” and agrees to the Phrases & Circumstances
2. Purchaser enters preliminary buy data
   
   1. Purchaser enters the quantity of ether they’d wish to buy
   2. Purchaser enters e mail deal with because the vacation spot for pockets backup file
   3. Purchaser enters passphrase, which serves as an encryption seed. A really robust passphrase is very advisable

3. Purchaser generates entropy by shifting their mouse or tapping their display screen. A “seed” is constructed based mostly on this generated entropy in addition to different random system inputs. When the specified entropy size is achieved the pockets is generated utilizing the seed.  The pockets incorporates:
   
   1. a person BTC deal with to ship the funds to
   2. a person ETH deal with
   3. an encrypted seed
   4. a backup encrypted seed

4. The browser sale app checks the newly created BTC deal with to see if funds arrive. Earlier than sending any funds, the client has a chance to obtain the pockets. If an issue happens between transactions, any funds ship to the client’s private deposit deal with might be accessible with the passphrase. If the unspent steadiness of the BTC deal with > 0.01 BTC, the browser sale app generates a signed transaction from the newly created BTC deal with with 2 particular outputs:
   
   1. an output of the whole unspent steadiness minus miners price to the primary sale BTC deal with–this btc deal with is the place all of the funds go, it’s a set, identified BTC deal with.
   2. an output of 10000 satoshi to a BTC deal with generated from the (string) ETH deal with–this bitcoin deal with is for confirming ethereum addresses and is exclusive for each transaction.

5. The browser sale app prompts the purchaser to obtain their pockets once more & and in addition sends the client an e mail containing a backup for the ether pockets.  The identical warning as said above applies.  Don’t go away the pockets as an e mail attachment in an e mail system.  Obtain as quickly as attainable and make sure that the e-mail is expunged.
6. The browser sale app will show the variety of bitcoin transaction confirmations

In order that’s it! Though there’s a whole lot of technical issues taking place within the background, the GUI we’ve got developed will make the method a click on by click on operation.