Wall Street tactics akin to the ones that fostered subprime mortgages in America have worsened the financial crisis shaking Greece and undermining the euro by enabling European governments to hide their mounting debts. As worries over Greece rattle world markets, records and interviews show that with Wall Street's help, the nation engaged in a decade-long effort to skirt European debt limits. One deal created by Goldman Sachs helped obscure billions in debt from the budget overseers in Brussels. As in the American subprime crisis and the implosion of the American International Group, financial derivatives played a role in the run-up of Greek debt. Instruments developed by Goldman Sachs, JPMorgan Chase and a wide range of other banks enabled politicians to mask additional borrowing in Greece, Italy and possibly elsewhere. In dozens of deals across the Continent, banks provided cash upfront in return for government payments in the future, with those liabilities then left off the books. Greece, for example, traded away the rights to airport fees and lottery proceeds in years to come. Critics say that such deals, because they are not recorded as loans, mislead investors and regulators about the depth of a country's liabilities.