Patent ID: 8135648

Claim:
A method of authenticating a document from a wagering game machine, comprising: receiving credit information by a server, the credit information including information indicating a player's balance at the wagering game machine; creating, by the wagering game machine, a security key for the document, wherein the document is a wagering receipt, lottery ticket, or wagering machine credit voucher; creating, by the wagering game machine, a secured document token by encrypting a document token including the credit information with the security key; sending, by the wagering game machine, the secured document token to the server; sending, by the wagering game machine, a credit response from the server; creating, by the wagering game machine, a modified security key by combining the credit response with the security key; providing, by the wagering game machine, the document including the credit information, the credit response and the modified security key; receiving, by a redemption device, a request to redeem the document for at least one of cash or game credit; receiving, by the redemption device, the modified security key from the document; retrieving, by the redemption device, the credit information, the secured document token, the document token and the credit response corresponding to the document; obtaining, by the redemption device, a candidate security key from the modified security key received from the document by removing the retrieved credit response from the modified security key received from the document; obtaining, by the redemption device, a candidate secured document token by encrypting the retrieved document token using the candidate security key; determining, by the redemption device, whether the obtained candidate secured document token matches the retrieved secured document token; and indicating, by the redemption device, the document is authentic based on the determination of the matching.