Kim Kardashian: Affair While Engaged To Kris Humphries? -- Convict's A Scumbag

Kim Kardashian did NOT bang a convict while she was engaged to Kris Humphries ... and the con is nothing but a swindler and liar ... so says Kim's lawyer in a scathing letter.

Andrey Hicks sent a website an email he claimed was written by Kim herself, admitting the two had an affair in Monaco shortly before her wedding to Kris ... and it was "a mistake."

Now Kim's lawyer, Marty Singer, has sent Andrey -- better known as inmate #21236-055 -- a letter ripping into him, calling him "a swindling convict and a liar," adding Andrey has even called himself "a greedy capitalist who went to jail for a greedy scheme."

In fact ... Andrey is a greedy capitalist who went to PRISON for a greedy, hedge fund scheme.

As for the email, Singer says the email is fake ... and Kim never ever sent it.

Here's the best part. Singer calls Andrey out for claiming he got a Ph.D in mathematics from Harvard, saying, "...you dropped out of Harvard after three semesters and earned a D- in the only math course you took at Harvard."