Patent ID: 11968191
Assignee: AMERICAN EXPRESS TRAVEL RELATED SERVICES COMPANY, INC.
Field: Digital communication (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 0:
1. A method comprising:
retrieving, by a user device, an encrypted session key through a network in response to: (i) determining a stored session key associated with a transaction account is set to expire in a threshold time period or (ii) detecting a number of session keys stored in the user device is below a threshold;
establishing, by the user device, a wireless connection with a point of sale terminal for a purchase;
generating, by the user device, a cryptogram from a decrypted session key based at least in part on the user device being disconnected from the network, the cryptogram being generated by:
generating a dynamic key based at least in part on a data encryption key;
decrypting a token using the dynamic key;
generating an operator value by applying an operator to the token and a random number;
generating the decrypted session key by decrypting the encrypted session key using the dynamic key; and
generating the cryptogram based at least in part on an encryption of the operator value using the decrypted session key; and

sending, by the user device, the cryptogram to the point of sale terminal, wherein the cryptogram is used to authorize the purchase through the wireless connection between the user device and the point of sale terminal.