Method and system for storing, retrieving, and managing data for tags
This invention relates generally to a method and system for storing, retrieving, and managing data for tags that are associated in some manner to any type of object. More particularly, the present invention writes data to these tags, reads data from these tags, and manages data that is written to and/or read from these tags.
1. A method for maintaining proximity of one or more tags comprising:
receiving a first message on a tag that includes a tag audible alarm, that is broadcast at a regular time interval from a partner tag that includes a partner tag audible alarm using a partner timer interrupt on the partner tag, and that includes a partner identifier of the partner tag that is used to distinguish the partner tag from other tags and a first broadcast time that is the time the first message is broadcast from the partner tag;
reading the partner identifier and the first broadcast time of the partner tag from said first message on the tag;
resetting tag alarm counter on the tag for said read partner identifier at the same regular time interval using a timer interrupt on the tag only if the first broadcast time in the first message is within a predetermined time period in order to prevent a replay attack;
broadcasting from the tag a second message that includes an identifier of the tag and a second broadcast time that is the time the second message is broadcast from the tag at the same regular time interval using the timer interrupt on the tag that the partner tag receives and uses to reset a partner tag alarm counter on the partner tag only if the second broadcast time in the second message is within the predetermined time period in order to prevent a replay attack;
sounding an alarm on the tag audible alarm of the tag when the tag alarm counter exceeds the regular time interval before the tag receives a third message from the partner tag; and
sounding an alarm on the partner tag audible alarm of the partner tag when the partner tag alarm counter exceeds the regular time interval before the partner tag receives a fourth message from the tag.
2. The method for maintaining proximity of one or more tags as in claim 1 wherein said resetting step is performed only if a signature of said read tag partner identifier in said first message verifies.
3. The method for maintaining proximity of one or more tags as in claim 1 wherein said predetermined time period is not more than one minute from a current time.
4. The method for maintaining proximity of one or more tags as in claim 1 further comprising:
if the first message is not received on the tag incrementing the tag alarm counter on the tag at the same regular time interval using the second timer interrupt on the tag;
sounding an alarm on the tag audible alarm of the tag if the tag alarm counter is greater than a predetermined limit;
if the second message is not received on the partner tag incrementing the partner tag alarm counter on the partner tag at the regular time interval using the partner timer interrupt on the partner tag; and
sounding an alarm on the partner tag audible alarm of the partner tag if the partner tag alarm counter is greater than the predetermined limit so that destroying one of the tag or the partner tag sounds an alarm on one of the tag or the partner tag.
5. The method for maintaining proximity of one or more tags as in claim 4 wherein said incrementing steps and said sounding steps are performed only when the timer interrupt on the tag is enabled and the partner interrupt on the partner tag is enabled.
6. The method for maintaining proximity of one or more tags as in claim 1 wherein one or both of the tag and the partner tag are tamper resistant to prevent one tag from repudiating contact with another tag.