A Study Of Secure Access And Self-destruction For Document In Cloud Computing

The release of cloud services, the interaction between cloud services and users, thecombination and coordination among various services and the realization of informationdissemination and sharing, etc, all of them can’t be survival without data carriers in thecloud computing. Structured document and composite document, as an emergingnetwork information form in the cloud computing environment, are just the demandingdata medians to achieve the referred goals. Therefore, it’s obvious that they haveextensive application value. However, in the cloud computing environment, we lack forthe valid structured document model and composite document model, the hierarchicalsafety protection scheme for document elements and the document’s whole life cyclesensitive information defense mechanism. Therefore, it’s especially important to studythe structured document model and composite document model which are adapted to thecloud environment. In addition, the security access and secure destruction mechanismare quite vital.In this dissertation, we have completely and systematically studied the structureddocument and composite document model, fine-grained access control mechanisms andsecure self-destruction schemes. The main contributions are as follows:1. We study the structured document model and its security access mechanism inthe cloud environment. We propose a description of the specific ‘‘live’’ characteristics ofthe structured document and establish an SDoc model to meet such characteristics.Based on a core component specification, we present a standardization description ofthe structured document, which can effectively solve the reuse and interoperabilityproblems among different organizations. Under the adequate consideration of role, time,environment and other contextual information and with the action-based access controland the multilevel security theory, we propose an AMAC scheme, which means amultilevel access control scheme based on the access actions of the users. Meanwhile,we attain the goal of classification security access for document elements. Furthermore,we prove the safety of the scheme with the information flow noninterference theory.2. We study the composite document model and its security access scheme in thecloud environment. On the basis of the structured document model, we propose a formaldescription of the composite document (ComDoc), which is according to the correlationof structured document’s elements and the multilevel security mechanism. To solve thecomplex key and certificate management problems in the PKI mechanism, we presentan ICDAC scheme, which is a composite document fine-grained access control scheme based on the identity-based encryption (IBE). By encapsulating the symmetric key ofthe encrypted composite document elements with the IBE, we can maintain hierarchicalsecurity protection and fine-grained access control to the elements in terms of theidentity information and access permissions of the authorized user. Comprehensiveanalysis shows that compared with the existing solutions, our scheme can simplify thekey management, reduce memory overhead and support the fine-grained access controlto the document elements.3. The composite document workflow across multiple security environments in theinsecure channel has the problem of the leakage of document participants’ identityprivacy and the forbidden to revoke participants’ privilege. In attempt to address suchproblem, based on the ComDoc model and combined with a threshold attribute basedencryption (TABE) algorithm, we propose a TACD scheme, which is a security accessscheme to the composite document based on the TABE. Through TABE, we are able topreserve the document participants’ identity privacy. The safety of document contentcan be guaranteed by the ComDoc model. To revoke participants’ privilege, we updatethe attribute and re-encrypt the document. Comprehensive analysis shows that ourproposed TACD scheme can meet the security requirements of the composite documentworkflow, has high efficiency and support fine-grained secure access to compositedocument elements.4. We analyze the safety self-destruction scheme after the expiration time of thestructured document. Aiming at solving the leak of the sensitive information containedin the structured document which stored in cloud services, we come up with a SDSSscheme (structured document secure self-destruction with IBE). We set a life cycle forthe SDoc and make use of the symmetric key encrypting structured document elements,and we can obtain a ciphertext. Then, we split it into extraction ciphertext andencapsulation ciphertext through the extraction algorithm. Meanwhile, we encrypt thesymmetric key through the IBE and acquire the key’s ciphertext, then mix it with theextraction ciphertext through the secret sharing scheme. Then, we are able to create amixture ciphertext shares and distribute the shares into a large-scale distributed DHTnetwork. Encapsulation ciphertext is encapsulated into structured document secure self-destruction objects and saved in cloud services. After a desired period of time, the DHTnetwork nodes will automatically discard the mixture ciphertext shares. Therefore, theoriginal document elements become unrecoverable. And we are able to realize thesecure self-destruction function. Comprehensive analysis shows that, the SDSS scheme satisfies the security requirements, can ensure the fine-grained access control in the lifecycle of the structured document, self-destruct after a specified time and be able to resistagainst the traditional cryptoanalysis attacks and the Sybile attacks in the DHT network.5. We research the composite document’s self-destruction after the expiration timein the composite document workflow. By integrating the ABE and DHT network intothe creation and processing of the composite document workflow, we propose a DWSSscheme, which is a secure self-destruction of the composite document workflow basedon the ABE algorithm. It can deal with the problems of the secure access, identityprivacy protection of the participants and sensitive information after the expiration timein the course of the composite document workflow in cloud computing environment.The DWSS scheme is based on the ComDoc. We encrypt the ComDoc elements with anaccess key, and encrypt it with the ABE, then in the process of extraction andconversion we can get ciphertext shares and encapsulated self-destruction objects.Meanwhile, we store them into two DHT networks and cloud services. After thepredefined time of the composite document workflow, the DHT network willautomatically discard the ciphertext shares and we can’t recover the original compositedocument ciphertext and the access key. Therefore, we achieve the purpose of secureself-deletion. Security analysis shows that, compared with existing schemes, our schemeis able to resist aginst the traditional cryptanalysis attacks and the Sybile attacks in theDHT network, supports the identity privacy protection of participators in the process ofworkflow and fine-grained access control in the life cycle and secure self-destructionafter the specified time of composite document.