Contactless card with multiple rotating security keys

A server comprising:

• a processor and a memory, the memory storing a first plurality of keys, a first input value, a key selection algorithm configured to select one of the first plurality of security keys based on the first input value, and a first encrypted communication from a contactless card,
• wherein the contactless card includes a card processor and a card memory, the card memory storing the first plurality of security keys, the key selection algorithm, and the first input value, and
• wherein the server is configured to:
• update the first input value to derive a second input value using a first number derived from a first transaction associated with the contactless card;
• select a first selected key using the key selection algorithm and the updated input value, the first selected key being one of the first plurality of keys;
• and
• decrypt the first encrypted communication using the second selected key to obtain a first unencrypted communication.

A method performed by a server comprising a processor and a memory, the memory storing a first plurality of keys, a first input value, a key selection algorithm configured to select one of the first plurality of security keys based on the first input value, and a first encrypted communication from a contactless card, the method comprising:

• updating the first input value to derive a second input value using a first number derived from a first transaction associated with the contactless card;
• selecting a first selected key using the key selection algorithm and the second input value, the first selected key being one of the first plurality of keys;
• and
• decrypting the first encrypted communication using the second selected key to obtain a first unencrypted communication,
• wherein the contactless card includes a card processor and a card memory, the card memory storing the first plurality of security keys, the key selection algorithm, and the first input value.

A contactless card comprising:

• a memory containing one or more applets, a counter value, a plurality of keys, and a key selection algorithm configured to select one of the first plurality of keys based on the counter value;
• a transceiver;
• and
• a processor in communication with the memory and the transceiver;
• wherein the processor is configured to:
• increment the counter value when the transceiver is within a range of a communication field of a client device;
• select a first selected key using a key selection algorithm stored on the memory;
• generate a communication;
• encrypt the communication using the first selected key to obtained an encrypted communication;
• and
• transmit, via the transceiver, the encrypted communication to the client device.