Browse Prior Art Database

Transaction Variant Encryption Keys in EFTPOS

IP.com Disclosure Number: IPCOM000035147D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Smith, PR: AUTHOR

Abstract

In Electronic Funds Transfer Point of Sale Systems (EFTPOS) it is required that Personal Identification Number (PIN) values should be entered on a PIN pad and encrypted with maximum security. In the system disclosed the encryption key values change after each transaction in a synchronized manner between partner or standby Hardware Security Module (HSM). When it is necessary to communicate transaction variant key values to an alternative (HSM), a new sequence of key values is started common to both HSMs. The key values are generated as sequences by predetermined functions from a seed value derived from a master seed value.

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Transaction Variant Encryption Keys in EFTPOS

In Electronic Funds Transfer Point of Sale Systems (EFTPOS) it is required that Personal Identification Number (PIN) values should be entered on a PIN pad and encrypted with maximum security. In the system disclosed the encryption key values change after each transaction in a synchronized manner between partner or standby Hardware Security Module (HSM). When it is necessary to communicate transaction variant key values to an alternative (HSM), a new sequence of key values is started common to both HSMs. The key values are generated as sequences by predetermined functions from a seed value derived from a master seed value.

In EFTPOS systems the PIN pad must be a low-cost unit installed in unsecured environments, so there is the additional real danger that the value of a PIN encrypting key can be obtained by a determined attack on a PIN pad.

This leads to the following requirements:- The PIN enciphering key value must be changed by an irreversible process following each encipherment. No value must remain in the PIN pad which could permit the value of any previous PIN enciphering key to be deduced as a result of a physical attack on the PIN pad and using a recording of messages from/to the PIN pad over an arbitrarily long period of time. Construction of the PIN pad must be such that the likelihood of successful penetration is low, and if penetrated the likelihood of putting the PIN pad back into service without detection is very low.

The system is outlined by the attached diagram. A PIN pad is equipped with a key store and encryption processor contained in a tamper resistant module, and is required to communicate with an unspecified number of HSMs for the purpose of transmitting PIN values for processing within the HSM. The system operates normally with the PIN pad communicating to one HSM, or to a number of HSMs which share cryptographic key information, and switches to an alternative HSM only when there is failure to communicate. Initial keying values are installed in each HSM by manual key-entry of values or exchange of values secured by encipherment under interchange encryption key values. Each HSM has a key store and encryption processor. A secure initialization facility is used to install values securely into PIN pad key storage and communicate the same values to the HSMs.

The PIN value is enciphered at the PIN pad and communicated to one HSM where it will be checked or further transformed. The 'Seed values' defined as follows:- A seed value is an initial value which may be used to generate the initial value of a sequence of successive values. The initial value is obtained by application of a one-way function to the seed value and the successive values are obta...