The integrity or the signator of an electronic document can be verified by embedding a security object, for example, supported by an object linking and embedding (OLE) capability, in the electronic document at a location selected by the signator. The embedded security object includes security information and an identifier for invoking the processing of the security information. The security information may include a document digest that characterizes the electronic document at the time the security object was embedded, a signature digest that identifies the signator and that characterizes the instance of the embedded security object, and the signator's electronic chop, which may be the signator's digitized signature or other graphic image. In addition, the security information can be encrypted using either private key encryption or public key encryption. When the electronic document is later displayed, the identifier invokes processing that decrypts the security information and calculates the document digest based on the current state of the electronic document. The signator of the electronic document can be verified based upon the result of the decryption. The integrity of the electronic document can be verified if the decrypted document digest matches the calculated document digest. If the signator and the document integrity are confirmed, the electronic chop is displayed in the document. If, however, the signator or document integrity are not verified, the electronic chop is not displayed. In addition, a warning message may be displayed if verification fails.

Electronic document verification system and method

A method and device for reliably assessing the integrity of a computer system's software prevents execution of corrupted programs at time of system initialization, enhancing system security. Programs and data comprising the system's trusted software, including all startup processes, are verified before being utilized. Methods to verify the trusted software use a hierarchy of both modification detection codes and public-key digital signature codes. The top-level codes are placed in a protectable non-volatile storage area, and are used by the startup program to verify the integrity of subsequent programs. A trusted initialization program sets a hardware latch to protect the codes in the non-volatile memory from being overwritten by subsequent untrusted programs. The latch is only reset at system restart, when control returns to the bootstrap program. Software reconfiguration is possible with trusted programs that write new top-level codes while the latch is open. The mechanism itself is immune to malicious software attack when the write-protect latch is closed before running untrusted software. Preferred embodiments in an IBM-compatible personal computer uses the reset switch to initiate a trusted path between the user and a program. Damage from certain classes of computer virus and trojan horse attacks is prevented. A system recovery process is described. A related improved method for user authentication uses a read-and -write memory protection latch to prevent access to sensitive authentication data.

Method and apparatus for assessing integrity of computer system software

To establish that a document was created after a given moment in time, it is necessary to report events that could not have been predicted before they happened. To establish that a document was created before a given moment in time, it is necessary to cause an event based on the document, which can be observed by others. Cryptographic hash functions can be used both to report events succinctly, and to cause events based on documents without revealing their contents. Haber and Stornetta have proposed two schemes for digital time-stamping which rely on these principles [HaSt 91].

Improving the Efficiency and Reliability of Digital Time-Stamping

A certification or signing method ensures the authenticity and integrity of a computer program, an executable file, or code received over a computer network. The method is used by a publisher or distributor to "sign" an executable file so it can be transmitted with confidence to a recipient over an open network like the Internet. The executable file may be of any executable form, including an executable or portable executable .exe file format, a .cab cabinet file format, an .ocx object control format, or a Java class file. The code signing method assures the recipient of the identity of the publisher as the source of file (i.e., its authenticity) and that the file has not been modified after being transmitted by the publisher (i.e., the integrity of the file). As a result, the code signing method allows an executable file to be transmitted over open computer networks like the Internet with increased certainty in the identity of the source of the file and minimized risk of contracting a computer virus or other malicious executable computer files.

Code certification for network transmission

A security enhanced computer system arrangement includes a coprocessor and a multiprocessor logic controller inserted into the architecture of a conventional computer system. The coprocessor and multiprocessor logic controller is interposed between the CPU of the conventional computer system to intercept and replace control signals that are passed over certain of the critical control signal lines associated with the CPU. The multiprocessor logic controller arrangement thereby isolates the CPU of the conventional computer system from the remainder of the conventional computer system, permitting separate control over the CPU and separate control over the remainder of the computer system. By controlling the control signals that are normally passed between the CPU and the remainder of the computer system, the multiprocessor logic controller permits the coprocessor to perform highly secure operations. These secure operations, selectable by a trusted operator or built in to a cooperating operating system, verify that the computer system is a trusted computing base which can be relied upon to perform its operations properly and without compromise.

Method and apparatus for enhancing computer system security

A cryptographic method and apparatus are disclosed which transform a message or arbitrary length into a block of fixed length (128 bits) defined modification detection code (MDC). Although there are a large number of messages which result in the same MDC, because the MDC is a many-to-one function of the input, it is required that it is practically not feasible for an opponent to find them. In analyzing the methods, a distinction is made between two types of attacks, i.e., insiders (who have access to the system) and outsiders (who do not). The first method employs four encryption steps per DEA block and provides the higher degree of security. Coupling between the different DEA operations is provided by using the input keys also as data in two of the four encryption steps. In addition, there is cross coupling by interchanging half of the internal keys. Although this second coupling operation does not add to security in this scheme, it is mandatory in the second method, which employs only two encryption steps per DEA block to trade off security for performance. By providing key cross coupling in both schemes, an identical kernel is established for both methods. This has an implementation advantage since the first method can be achieved by applying the second method twice. The MDC, when loaded into a secure device, authorizes one and only one data set to be authenticated by the MDC, whereas methods based on message authentication codes or digital signatures involving a public key algorithm authorize a plurality of data sets to be authenticated. The MDC therefore provides for greater security control.

Shaiy Pilpel

Papers

Data authentication using modification detection codes based on a public one way encryption function