Importance

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Abstract

In order to achieve very secure transmission of sensitive information over a public communications medium such as the Internet to carry out transactions therebetween, an account initialization data set is developed in a client system and duplicated, by secure means, in a host system. At each of the client and host systems, an initial client control file data set including a plurality of control fields (at least one of which includes data developed from information which is unique to the client system hardware) is independently developed and stored using functionally identical algorithms and incorporating information included in at least a part of the account initialization data set. Subsequently, during initiation of a transaction, a validation string generated from a plurality of the client control file data set fields stored in the client system and at least one additional field containing transaction specific information is sent from the client system to the host system over an insecure transmission medium such as the Internet. At the host, a validation string is generated using the corresponding control file data set fields, identically manipulated, and the apparent client generated and host generated initial validation strings are checked for identity. If the initial validation strings are identical, the transaction is carried out; however, if the initial validation strings are not identical, the transaction is aborted. Assuming that the transaction is carried out, updated client control file data sets, which are identically modified according to a predetermined modification procedure from the previous client control file data sets, based on new information which is specific to the transaction just carried out, are independently developed and stored at each of the client and host systems to be used to validate the next transaction.

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First Claim