Communications security and trusted path method and means

Abstract

A trusted path device is described which may be used stand alone or may be retrofitted to a users untrusted computer console or workstation so that an untrusted data input may be displayed on an untrusted display and verified by the user, following which the trusted data can be output to an untrusted or trusted device or network. The output may be encrypted or not, by means of an encryption device which may or may not use a 'one time pad' key provided from a structured array of retrievable “one time pad” keys having associated uniquely there with, a serial number which itself need not be encrypted but with which the input data and encrypted output data are uniquely associated. Sufficient “one time pad” keys are provided on a commonly available and physically manageable medium so as to allow much simplified key management procedures while still maintaining high levels of correctness and effectiveness of the encryption processes. Trusted devices as per ITSEC Level 6 may be used to implement the trusted path and encryption devices since the apparatus according to the invention are inherently simple in functionality thereby simplifying conformance with the relevant ITSEC and security equivalent requirements.