WEthereum API

Haskell based API that returns a payout for weather insurance.

Usage

Setup

Run the command runghc server.hs. Requires Haskell.

Personal Setup

• This API requires a WeatherUnderground API key. A developer key, with a limited number of requests per day is available for free on the WUnderground website. You will need to edit server.hs so that wuApiKey refers to your key.
• Set secretKey to your own (actually secret) secret 256 bit key.
• Set Happstack.Lite.port to the port of your choice. Change 8000 in the url provided to your chosen port.
• In calculatePayout, change the transaction fee from 50000000000000000 to your own transaction fee.
• In calculatePayout, change the payout amount from 0.9 to your own payout amount. This number must be less than 1. Decreasing the value reduces the payout, increasing your cut.

Input

Queries are made to url:8000/api/timeInsuredFor/latitude/longitude/initialAmout where:

• timeInsuredFor is a unix timestamp of the format 1234567890. It must refer to a time in the future (i.e. it must be a positive numerical value greater than the current number of seconds since 1st January 1970), otherwise no response is provided by the server.
• latitude is a signed numerical value between -180 and +180. E.g. 51.5074. Value is in degrees. Positive means North, negative means South.
• longitude is a signed numerical value between -180 and +180. E.g. -0.1278. Value is in degrees. Positive means East, negative means West.
• initialAmount is a positive integer. E.g. 1000000000000000000. It gives the initial insurance payment. The intended currency is wei (the smallest unit of Ether).

Example: url:8000/api/1234567890/51.5074/-0.1278/1000000000000000000 represents an insurance contract, requested for the 13th February 2009, in London (51.5074° N, 0.1278° W), with an initial payment of 1 Ether. (Note that this is not a valid input, however, as the date is in the past).

Important Input Requirements

• The timestamp provided must be in the future, or no response will be given.
• In certain cases, if the coordinates are too far from an airport weather station, no response will be given.

Ouput

Outputs are given in the format payout,initialAmount,latitude,longitude,timeInsuredFor,currentTime,hash where:

• payout is the fair payout calculated by the API. The intended currency is wei. The payout calculation deducts a cut of 50000000000000000 units (equivalent to 0.05 ether in the intended currency) to cover transaction fees, and then calculates a payout based on the probability of precipitation, taking a further cut which is equivalent to a 10% cut in the probability.
• initialAmount is the input initialAmount.
• latitude is the input latitude.
• longitude is the input longitude.
• timeInsuredFor is the input timeInsuredFor.
• currentTime is the current unix timestamp, truncated to an integral value.
• hash is a secp256k1 signature based on a sha256 hash of all of the data which precedes it (i.e. payout,initialAmount,latitude,longitude,timeInsuredFor,currentTime,hash - note that it includes all commas except the final one).

Probability Calculation

If the date to insure for is within 10 days of the current date, a forecasted probability is used. Otherwise, the probability is determined from historical values.