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Security module for an electronic funds transfer system

  • US 4,731,842 A
  • Filed: 12/10/1985
  • Issued: 03/15/1988
  • Est. Priority Date: 12/12/1984
  • Status: Expired due to Term
First Claim
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1. A security module, for authenticating messages having a plurality of different formats and cryptographic authenticators, contained in a tamper-resistant housing and including two data input devices, a display unit, at least one input/output port for connecting the module to an external processor and a security controller, characterised in that the security controller includes:

  • at least one read only memory which stores a state table and a module master encryption key;

    a control logic unit including a microprocessor and a control store which stores a plurality of different control function routines invoked by different entries in the state table;

    function key generation means to generate different encryption keys dependent upon a particular control function and a derivative of the module master key; and

    means to perform encryption and decryption operations on messages transmitted to and from the module using keys transmitted to the module encrypted under one of a number of derivatives of the module master key to authenticate said messages;

    whereby data input to the module at the first of the two data input devices is used to determine the control function routine that the module is to perform and the encryption key used to encode data input at the second data input device.

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