Pers Ubiquit Comput(2007)11: 157-169 Fig. 3 MobiPass format <mobiPass> <ecaID>SYDAU102. 23474</ecaID> <location>cr: //paramatta. nsw. au. mobipass com</location> <mobiPolicy> <policylD>1223-3328-.24</policyID> <location>paramatta.nsw.au.mobipass.com</location> mobiPolicy> <expireAt1124030906734</expireAt> <certified> <business Name>UTD Furniture Sydney</businessName> K <non Certified>..</non Certified> <certifiedDigestf5f7f7.8a53</certifiedDigest> <mobiPassDigest>6fh7fl. da84</mobiPassDigest> <timestamp> <not Before>1132622517640</not Before> <not After>l 132622519640</not After> </mobiPass> of not After and not Before will be fairly small to get requirements, and how sensitive the data is inside the maximum security. MobiPass. and it is also renewable Mobile entities can Here it must be noticed that if the first digit of the renew their MobiPass at any time to prevent the ECA-ID is 0, then the location(URI) of the ECA must expiration and increase their degree of trustworthiness be in the sub-domain of the Cr(mobipass org in our case), and the same for the MobiPolicy. Furthermore, 2.2.5 MobiManager if the Policy-ID is registered (0 for the first digit), then MobiManager is a software package which has all the it can only be verified by the accredited ECA necessary functionalities to manage and process Mo- MobiPass can be regarded as a special form of dig- biPasses in our architecture For instance, the Mobi- ital certificate which carries necessary and context aware information for mobile entities. As such it does anager will parse the MobiPass, can contact the CR not just provide authentication as a normal certificate and automatically generate the preference selection does but also contains information to drive authoriza- interface for a MobiPass by referring to the schema in tion decisions the mobipolicy and so on. From Fig. 1, we can see that all mobile entities are virtually connected through the eCa by referring to 2.3 A trusted interaction using MobiPass the MobiPolicy in the ubiquitous computing environ ment. The MobiPass expires after a certain time In a highly dynamic and unpredictable ubiquitous depending on the functional and nonfunctional computing environment, it is neither efficient nor fea Sprof notAfter and notBefore will be fairly small to get maximum security. Here it must be noticed that if the first digit of the ECA-ID is 0, then the location (URI) of the ECA must be in the sub-domain of the CR (mobipass.org in our case), and the same for the MobiPolicy. Furthermore, if the Policy-ID is registered (0 for the first digit), then it can only be verified by the accredited ECA. MobiPass can be regarded as a special form of dig￾ital certificate which carries necessary and context aware information for mobile entities. As such it does not just provide authentication as a normal certificate does but also contains information to drive authoriza￾tion decisions. From Fig. 1, we can see that all mobile entities are virtually connected through the ECA by referring to the MobiPolicy in the ubiquitous computing environ￾ment. The MobiPass expires after a certain time depending on the functional and nonfunctional requirements, and how sensitive the data is inside the MobiPass, and it is also renewable. Mobile entities can renew their MobiPass at any time to prevent their expiration and increase their degree of trustworthiness. 2.2.5 MobiManager MobiManager is a software package which has all the necessary functionalities to manage and process Mo￾biPasses in our architecture. For instance, the Mobi￾Manager will parse the MobiPass, can contact the CR and automatically generate the preference selection interface for a MobiPass by referring to the schema in the MobiPolicy and so on. 2.3 A trusted interaction using MobiPass In a highly dynamic and unpredictable ubiquitous computing environment, it is neither efficient nor fea- <mobiPass> <eca> <ecaID>SYDAU102...23474</ecaID> <location>cr://paramatta.nsw.au.mobipass.com</location> </eca> <mobiPolicy> <policyID>1223-3328-...24</policyID> <location>paramatta.nsw.au.mobipass.com</location> </mobiPolicy> <expireAt>1124030906734</expireAt> ... <certified> <businessName>UTD Furniture Sydney</businessName> ...... ...... <publicKey>mQENBEJvo....</publicKey> </certified> <nonCertified>......</nonCertified> <certifiedDigest>f5f7f7...8a53</certifiedDigest> <mobiPassDigest>6fh7f1...cda84</mobiPassDigest> <timestamp> <notBefore>1132622517640</notBefore> <notAfter>1132622519640</notAfter> <signature>skz...==z</signature> </timestamp> </mobiPass> Fig. 3 MobiPass format 162 Pers Ubiquit Comput (2007) 11:157–169 123