These are the notes from my talk at the last meeting. They may only be parsable by people who saw the talk, but I'm interested in all comments. Thanks to Mark Miller and Eric Drexler who helped me put together these notes the first time. The need for reputations: single Prisoner's Dilemna incentive for defecting iterated Prisoner's dilemna incentive for cooperating reps put each person in an iterated situation with the group better reputations reduce reputation float (see below) Spreading reputations makes them better at encouraging cooperation Uses of reputations: sorting filtering - this is just bad sorting collateral - for business and important trust issues let me add that reputation appication is largely on the receiving side Negative reputations: don't work with anonymity because you just make another identity don't spread for psychological and legal reasons many people won't reveal negative opinions about others people primarily support filtering and collateral Positive reputations: are safer to reveal and spread allow sorting can handle anonymous pseudonyms Anonymity: reduces perceived and actual accountability breaks many of our trained intutions for trusting others implicit but unrevealed assets aren't at risk trade names are examples of non-anon. pseudonyms Reputations systems for sorting mail are less of an issues than reputations systems for actual business because there is less at risk. Gaming of a reputation system depends on how much is at risk. Brilliant Pennies: randomly generated reputations the con game: start with 1000 pennies flip them every day. head the stock market goes up, tails it goes down throw out pennies that 'guessed' wrong at the end of ten days you have a penny with a 'reputation' for predicting the stock market sell the penny anonymously :-) inconsistent positive reputations are better than perfect reputations can explain away first several mistakes Assets that support an identity recoverable assets anything that can be recovered in the even of a defection bank accounts, goods, factories, etc. pseudonyms typically won't have recoverable assets pseudonyms could keep recoverable assets in a non-anonymous escrow can be anonymously and privately committed to more than one party in the event of a defection, so value can't properly be assessed unrecoverable assets Sunk costs time, money spent building a reputation solves the Brilliant Penny problem: random rep requires huge investment a 30day coin-flipping rep requires more pennies than exist notarized money-destruction service: proves investment with no route for kickbacks to the investor demonstrates the comparative cost of running an anon. service our intuitions about sunk costs can be very wrong here we're used to sunk costs at least looking recoverable (liquidation) we're used to eventual personal accountability of decision maker sunk costs enable kill files again you can only afford so many pseudonyms this is relates to the Brilliant Penny solution reputation capital (perceived value of reputation) customer good will, market share, shelf space, customer mind-space, etc. priority settings in receivers's mail handlers (filters, sorters) future sales potential based on the net present value of the reputation perceived differently by different individuals (customers/producer) based on discount rate (subjective value of money now vs. money later?) perception of discount rate can change radically you are told you have 6 months to live Reputation Float: latency between use of a reputation and the effect on the value of the reputation how long can you ride on past glory? this includes the amount of goods, etc. against which the reputation is collateral existing trade-names collateralize the quality of existing goods (i.e. cars) estimating reputation float is a public goods problem why should I reveal the goods I have outstanding if I can get the info anyway insurance (Idea Futures) doesn't help the anonymous could collect both from defaulting and from insurance our intuitions screw up at estimating this we're not used to untraceable transactions Miscellaneous: filtering/sorting reputations should be wrt to topics This generalizes to other criteria individuals have different levels of expertise in different areas synthesized reputations are reputations composed from multiple reputations chaining remailers composes their reputations for security voting among key providers composes their uncompromisability reputations