11-08-2012, 11:30 AM
enhanced AES WITH BUILT IN SELF TEST CAPABILITY
ENHANCED AES WITH BUILT-IN SELF TEST CAPABILITY.doc (Size: 1.08 MB / Downloads: 41)
INTRODUCTION
Security is a protective measure or mechanism which ensures safety from intruders. Network security is mainly concerned with protection of networks and their services from unauthorized access, alteration and destruction. Many unauthorized people cause network security problems for gaining information about the other users or causing harm to them. Mainly the four security problems that occur in any network are as follows i.e secrecy, authentication, non repudiation, and integrity control.
Whether it is the electronic transfer of money, the electronic interchange of commercial information, or electronic email among friends, senders and receivers need to know that others cannot intercept or read their messages or transmit false messages in their place. This evaluation of dependence on information leads to the conclusion that now, more than ever, information is valuable, for not only how it is shared, but also how it is protected from others.
From e-mail to cellular communications, from secure web access to digital cash, cryptography is an essential part of today’s information systems. Cryptography helps to provide accuracy, confidentiality. It can prevent fraud in electronic commerce and assure the validity of financial transactions. It can prove your identity or protect your anonymity. It can keep vandals from altering web pages and prevent industrial competitors from reading your confidential documents. In addition, in the future, as commerce and communications continue to move to computer networks, cryptography will become more and more vital.
Today, encryption is one of the most popular and successful methods for protecting valuable information. Many insecure products have not yet been broken because they are still in their infancy but when these products are widely used, they will become tempting targets for criminals. The press will publicize the attacks, undermining public confidence in these systems. Ultimately, products will win or lose in the market place depending on the strength of their security.
The weak “crypto-algorithms”, poor design of the device or hardware physical failures can render the product insecure and place highly sensitive information at risk. Validation of crypto-algorithm and test of the hardware implementing such functions are essential.
This project aims at providing efficient test solution for the physical platform that implements the crypto-algorithm, i.e. the dedicated piece of hardware that executes the encryption.
Independently of the intended function, defects created during the manufacturing process of integrated circuit (IC) are unavoidable and some number of ICs is expected to be faulty. Post-manufacturing testing is thus required to guarantee fault free products. It’s all the more important for applications requiring digital security because a faulty chip could fail to protect the secret data.
Independently of the intended function, defects created during the manufacturing process of integrated circuit (IC) are unavoidable and some number of ICs is expected to be faulty. Post-manufacturing testing is thus required to guarantee fault free products. It’s all the more important for applications requiring digital security because a faulty chip could fail to protect the secret data.
Due to the extremely large number of possible defect types and defect locations, fault models are used for computational efficiency during fault simulation and test stimuli generation. A combination of different fault models is generally used in the evaluation of testing approaches; among them the stuck-at fault model remains inescapable.
Detection of such faults generally requires test oriented design methodology that aim to facilitate generation of proper test stimuli. Scan design is the most widely used structured Design-for-Testability (DFT) methodology. While it greatly facilitates the test of the IC and minimizes the probability to deliver faulty chips, it compromises the security of the system since it provides facilities for controlling or observing sensitive data.
The Built-In Self-Test (BIST) approach does not require visible scan chains. The test patterns are classically generated on chip by an additional Test Pattern Generator (TPG) and test responses are compacted into a signature before comparison with the pre-computed golden one with the help of a Signature Analyzer (SA). The result of the comparison is the only test output. This test strategy is a good alternative if it provides low area overhead and acceptable fault coverage. Note that apart from its recurrent cost, extra silicon area for BIST may in turn be subject to faults. As usual, additional hardware for BIST implementation must be kept as low as possible.
Apart from its recurrent cost, extra silicon area for BIST may in turn be subject to faults. As usual, additional hardware for BIST implementation must be kept as low as possible. In order to save TPG and SA related area overheads, we propose a BIST methodology specifically designed for block-cipher circuits. The proposed BIST technique incurs almost no area overhead.
CRYPTOGRAPHY
The fundamental objective of cryptography is to enable two people to communicate over an insecure channel in such a way that an opponent cannot understand what is being said. The information or message to be sent in plaintext. The process of disguising a message in such a way as to hide its substance in ENCRYPTION. An encrypted message is CIPHERTEXT. The process of turning ciphertext back into plaintext is DECRYPTION.
The art and science of keeping messages secure is cryptographic, and is practiced by cryptographers. Cryptanalyst are practitioners of cryptanalysis, the art and science of breaking ciphertext, which is seeing through the disguise. The branch of mathematics encompassing both cryptography and cryptanalysis is CRYPTOLOGY.
HISTORY
Cryptography has a long and fascinating history. Cryptography has its initial and limited use by the Egyptians some 4000 years ago, to the twentieth century where it played a crucial role in the outcome of both world wars. Completed in 1963, Kahn’s book covers those aspects of the history which were most significant (up to that time) to the development of the subject. The predominant practitioners of the art were those associated with military, the diplomatic service and government in general. Cryptography was used as a tool to protect national secrets and strategies.
The proliferation of computers and communications systems in the 1960’s brought with it a demand from the private sector for means to protect information in digital form and to provide security services. Beginning with the work of Feistel at IBM in the early 1970’s a culminating in 1977 with the adoption as a U.S Federal Information Processing Standard for encrypting unclassified information, Data Encryption Standard, is the most well-known cryptographic mechanism in history. It remains the standard means for securing electronic commerce for many financial institutions around the world.
The most striking development in the history of cryptography came in 1976 when Diffie and Hellmann published New Directions in Cryptography. This paper introduced the revolutionary concept of public-key cryptography and also provided a new and ingenious method for key exchange, the security of which is based on the intractability of discrete algorithm problem. Although the authors had no practical realization of a public-key encryption scheme at the time, the idea was clear and it generated extensive interest and activity in the cryptographic community. In 1978 Rivest, Shamir, and Adleman discovered the first practical public-key encryption and signature scheme. This scheme is based on another hand mathematical problem, the intractability of factoring large integers. This application of hard mathematical problem to cryptography revitalized efforts to find more efficient methods to factor.
ElGamal found another class of powerful and practical public-key schemes in 1985. These are also based on the discrete algorithm problem. One of the most significant contributions provided by public-key cryptography is the digital signature. In 1991, the first international standard for digital signature. In 1991, the first international standard for standard for digital signatures (ISO/IEC9796) was adopted. It is based on the RSA public key scheme. In 1994, the U.S. Government adopted the Digital Signature Standard, a mechanism based on the ElGamal public key scheme.
The search for new security schemes, improvements to existing cryptographic mechanisms, and proofs of security continues at a rapid pace. Various standards and infrastructures involving cryptography were being put in place. Security products were being developed to address the security needs of an information intensive society.
DEFINITION
A cryptosystem is a five-tuple(P,C,K,E,D) where the following conditions are satisfied.
1. P is a finite set of possible plaintext.
2. C is a finite set of possible ciphertext.
3. K, the key space, is a finite set of possibilities.
4. For each K ε K, there is an encryption rule Ek ε E and a corresponding decryption rule Dk ε D. Each Ek: P→C and Dk: C→P are functions such that Dk(Ek(X)) = X for every plaintext X ε P.
The main property says that if a plaintext X is encrypted using Ek, and the resulting ciphertext is subsequently decrypted using Dk, then the original plaintext X results. The plaintext can be a stream of bits, a digital video image or anything at all. As far as computer is concerned, X is simply binary data.
CRYPTOGRAPHIC GOALS
Cryptography is required to provide the following security services:
Privacy or confidentiality
Data integrity
Authentication
Non repudiation
1. Confidentiality: Confidentiality is a service used to keep the content of information secret from all but from those authorized to have it. Secrecy is a term synonymous with confidentiality and privacy. There are numerous approaches to providing confidentiality, ranging from physical protection to mathematical algorithms, which render data unintelligible.
2. Data Integrity: Data integrity is a service, which addresses the unauthorized alteration of data. To assure data integrity, one must have the ability to detect data manipulation by unauthorized parties. Data manipulation includes such things as insertion, deletion and substitution.
3. Authentication: Authentication is a service related to identification. This function applies to both entities and information itself. Two parties enter into a communication should identify each other. Information delivered over a channel should be authenticated as to origin, date of origin, data content, time sent, etc. For these reasons this aspect of cryptography is usually subdivided into two major classes: entity authentication and data origin authentication. Data origin authentication implicitly provides data integrity.
4. Non Repudiation: Non repudiation is a service, which prevents an entity from denying previous commitments or actions. When disputes arise due to an entity denying that certain actions were taken, a means to resolve the situation is necessary. For example, one entity may authorize the purchase of property by another entity and later deny such authorization was granted. A procedure involving a trusted third party is needed to resolve the dispute.