| ??? 03/29/05 21:11 Read: times |
#90632 - Challenge/response Responding to: ???'s previous message |
Prahlad J. Purohit said:
Dear Friends,
Have you ever faced a condition where in you sell a device on monthly installment payment term? And the customer doesnt give installment on time because his production is going on. What can one do to to avoid such problems. Well I am dealing with one such customer and looking at the ways for recovering money. Now I want to do something with my product so that they obey my order and stop working if the customer doesnt pay. How to do it? One way is using some Challenge code and Installment Code method. In this method the device will stop working after a preset period and display a "Random" Challenge code [preferably 5 digit code] and will ask for Installment code. We will issue the installment code upon receiving monthly installment. After keying in the installment code machine will go back to normal work and will popup simillar Random Challenge code when next installment is due. The Challenge codes could be generate by using Keil Psudo Random number generator function and there will be some mathamatical trick for example Swap the nibbles, rotate the bits, add, multiply etc to get Installment code from Challenge code. How good is this method? Are there any other better methods you are using? Thanks & Regards, Prahlad Purohit Prahlad J. Purohit said:
Dear Friends,
Have you ever faced a condition where in you sell a device on monthly installment payment term? And the customer doesnt give installment on time because his production is going on. What can one do to to avoid such problems. Well I am dealing with one such customer and looking at the ways for recovering money. Now I want to do something with my product so that they obey my order and stop working if the customer doesnt pay. How to do it? One way is using some Challenge code and Installment Code method. In this method the device will stop working after a preset period and display a "Random" Challenge code [preferably 5 digit code] and will ask for Installment code. We will issue the installment code upon receiving monthly installment. After keying in the installment code machine will go back to normal work and will popup simillar Random Challenge code when next installment is due. The Challenge codes could be generate by using Keil Psudo Random number generator function and there will be some mathamatical trick for example Swap the nibbles, rotate the bits, add, multiply etc to get Installment code from Challenge code. How good is this method? Are there any other better methods you are using? Thanks & Regards, Prahlad Purohit Prahlad J. Purohit said:
Dear Friends,
Have you ever faced a condition where in you sell a device on monthly installment payment term? And the customer doesnt give installment on time because his production is going on. What can one do to to avoid such problems. Well I am dealing with one such customer and looking at the ways for recovering money. Now I want to do something with my product so that they obey my order and stop working if the customer doesnt pay. How to do it? One way is using some Challenge code and Installment Code method. In this method the device will stop working after a preset period and display a "Random" Challenge code [preferably 5 digit code] and will ask for Installment code. We will issue the installment code upon receiving monthly installment. After keying in the installment code machine will go back to normal work and will popup simillar Random Challenge code when next installment is due. The Challenge codes could be generate by using Keil Psudo Random number generator function and there will be some mathamatical trick for example Swap the nibbles, rotate the bits, add, multiply etc to get Installment code from Challenge code. How good is this method? Are there any other better methods you are using? Thanks & Regards, Prahlad Purohit The standard way to implement this kind of thing is called a challenge/response protocol,there are many different methods but what you are trying to do is send your device a question which can only be answered if your device has a valid id,salt,serial-number whatever. One way is to use once again to use lsfr as in the keyloc devices used in car alarms.I wont go into detail because the full implementation is complex and if not done properly it wont work. |
