Efficient interaction processing using secret

A contactless access device comprising:

• a processor;
• and
• a computer-readable medium coupled to the processor, the computer-readable medium comprising code executable by the processor for implementing a method comprising:
• determining an interaction value associated with an interaction;
• responsive to determining the interaction value, prompting a user operating a user device for a secret;
• receiving the secret from the user;
• after receiving the secret from the user, receiving, from the user device, an initial communication from the user device over a wireless communication medium;
• receiving, from the user device, a user device certificate comprising a public key;
• verifying the user device certificate;
• concatenating at least the secret and an unpredictable number to form a concatenated value;
• encrypting the concatenated value with the public key;
• transmitting the encrypted concatenated value over the wireless communication medium to the access device, wherein the user device decrypts the encrypted concatenated value with a private key corresponding to the public key, verifies the unpredictable number, verifies the secret by comparing the 22 secret to another secret stored in the user device, determines whether or not the interaction is approved based at least upon the verification of the secret, produces a user device interaction authorization result, and then provides the user device interaction authorization result to the contactless access device;
• and
• receiving, from the user device, the user device interaction 27 authorization result.

A method comprising:

• upon entering communication range with a contactless access device during an interaction, providing, by a user device, an initial communication from the user device over a wireless communication medium;
• receiving, by the user device, a read record command from the contactless access device, wherein the read record command requests at least one or more certificates from the user device;
• obtaining, by the user device, at least the one or more certificates from memory;
• generating, by the user device, a read record response message comprising at least the one or more certificates;
• providing, by the user device, the read record response message to the contactless access device in response to the read record command, wherein the one or certificates includes a user device certificate comprising a public key, wherein the contactless access device verifies the user device certificate, concatenates at least a secret provided by a user of the user device to the contactless access device and an unpredictable number to form a concatenated value, encrypts the concatenated value with the public key, and transmits the encrypted concatenated value over the wireless communication medium to the user device;
• receiving, by the user device, the encrypted concatenated value from the contactless access device;
• decrypting, by the user device, the encrypted concatenated value using a private key corresponding to the public key;
• verifying, by the user device, the secret included in the concatenated value by comparing the secret to another secret stored in the user device;
• producing, by the user device, a user device interaction authorization result based on whether or not the interaction is approved based at least upon the verification of the secret;
• and
• providing, by the user device, the user device interaction authorization result to the contactless access device.