leo/examples/broken_bank

Blind Auction

A "broken" bank written in Leo.

Summary

A first-price sealed-bid auction (or blind auction) is a type of auction in which each participant submits a bid without knowing the bids of the other participants. The bidder with the highest bid wins the auction.

In this model, there are two parties: the auctioneer and the bidders.

• Bidder: A participant in the auction.
• Auctioneer: The party responsible for conducting the auction.

We make following assumptions about the auction:

• The auctioneer is honest. That is, the auctioneer will resolve all bids in the order they are received. The auctioneer will not tamper with the bids.
• There is no limit to the number of bids.
• The auctioneer knows the identity of all bidders, but bidders do not necessarily know the identity of other bidders.

Under this model, we require that:

• Bidders do not learn any information about the value of other bids.

Auction Flow

The auction is conducted in a series of stages.

• Bidding: In the bidding stage, bidders submit bids to the auctioneer. They do so by invoking the place_bid function.
• Resolution: In the resolution stage, the auctioneer resolves the bids in the order they were received. The auctioneer does so by invoking the resolve function. The resolution process produces a single winning bid.
• Finishing: In this stage, the auctioneer finishes the auction by invoking the finish function. This function returns the winning bid to the bidder, which the bidder can then use to claim the item.

Vulnerabilities

You may have already guessed that this program has a few vulnerabilities. Can you find them?

Language Features and Concepts

• record declarations
• console.assert_eq
• core functions, e.g. BHP256::hash
• record ownership
• loops and bounded iteration
• mappings
• finalize

Running the Program

Leo provides users with a command line interface for compiling and running Leo programs. Users may either specify input values via the command line or provide an input file in inputs/.

Configuring Accounts

The program.json file contains a private key and address. This is the account that will be used to sign transactions and is checked for record ownership. When executing programs as different parties, be sure to set the private_key and address fields in program.json to the appropriate values.

See ./run.sh for an example of how to run the program as different parties.

The Aleo SDK provides a command line interface for generating new accounts. To generate a new account, run

leo account new

Providing inputs via the command line.

1. Run

leo run <function_name> <input_1> <input_2> ...

See ./run.sh for an example.

Using an input file.

1. Modify inputs/auction.in with the desired inputs.
2. Run

leo run <function_name>

For example,

leo run issue
leo run deposit
leo run withdraw