Public key cryptography

Public key cryptography is fast becoming the foundation for on-line commerce and other applications that require security and authentication. The use of this kind of cryptography requires a public key infrastructure (PKI) to publish and manage public key values. To prepare the activities for the implementation of PKI features an evaluation of commercial hardware and software solutions is necessary. The implementation of PKI features generally can be divided into several steps  

The present concept deals with the first part of the entire PKI concept software evaluation, biometric device implementation, and biometric access control. 

In its most simple form, a PKI is a system for publishing the public key values used in public key cryptography. There are two basic operations common to all PKIs. Certification is the process of binding a public key value to an individual, organization, or other entity or even to some other piece of information, such as a permission or credential. On the other hand, validation is the process of verifying that a certificate is still valid. How these two operations are implemented is the basic defining characteristic of all PKIs. 

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Public-Key Cryptography Standards (PKCS) are a family of standards for public-key encryption developed by RSA Laboratories. It describes the syntax for a number of data structures used with public-key cryptography. 

In 1976, Whitfield Diffie developed public-key encryption as an alternative to private-key encryption. Public-key encryption is based on two halves of the same key that are generated with special software at the same time. The key pair are mathematically related so that the private key cannot be determined from the public key. Only one of the two halves of the key pair is required to encrypt a message, with the other half being used for decryption. In public key cryptography, one half of the key pair (the private key) is assigned to an individual, and is closely guarded and securely stored on the user s local disk in either an encrypted format or as part of a token that interfaces with the computer. The other half of the key is published in a public directory where all users can access it and this therefore referred to as the public key. 

Public-key cryptography, when properly implemented and used, enables people to communicate in secrecy, and to sign documents, with almost absolute security and without ever having to exchange a private key. 

RSA Laboratories, in collaboration with Apple, Digital, Lotus, Microsoft, MIT, Northern Telecom, Novell and Sun, developed a family of standards describing data structures used with public key cryptography. 

EvSY84 Shimon Even, Alan L. Selman, Yacov Yacobi The Complexity of Promise Problems with Applications to Public-Key Cryptography Information and Control 61 (1984) 159-173. 

In contrast with secret key cryptography, public key cryptography is based on separate encryption and decryption keys, where one of them can be published. Anyone can use that public key to encrypt a message that only the owner of the private key... 

The basic idea is to apply the principles of the bank s safety deposit box to an IT solution for safeguarding electronic patient records. For the provision of services for sealed/locked records, the asymmetric cryptography technology, also known as public key cryptography, can be exploited as the base technology for implementation of a system managing the sensitive information in a sealed or locked state, for protection of privacy and for prevention of identity theft in the electronic information age. 

As an analogy, think of the following scenario You manufacture multiple locks and an only key for those locks then you distribute the locks to your friends but keep the only key for yourself. When one of your friends wants to send you a secret letter, she will put the letter in a box and lock the box with your lock. Once it is locked, even your friend no longer can open the box because she does not have the key for the lock and because you have the only key for the lock. Therefore the box can be delivered safely to you even if you use some untrusted third party (e.g., courier, postman) for delivery. Only you can open the box with the only key you keep. Conversely, if you want to send a secret letter to your friend, you put your letter in a box and lock it with your friend s lock. Once locked, even you cannot unlock the box because your friend has the only key for the box. Consequently you are assured that only your friend can read your secret letter. Even if the box is misdelivered to someone else, the content of your letter is still kept secret because the box can be only opened by your friend, the friend you intended to access the secret letter. The key advantage of this asymmetric-key cryptography or public-key cryptography is that secret keys are kept with their owners and do not ever need to be shared with anyone else. 

Final Comment. The advent of the information and technology age requires quick and reliable transmission of data and information. Methods such as check digit schemes ensure that this is done confidentially and without error. Today s computer-reliant society uses the material developed in this book on a daily basis in all walks of life. This is illustrated by the simple procedure of sending a credit card number over the Internet. Not only do credit card numbers use the IBM check digit scheme presented in Chapter 3. but the RSA public key cryptography system is used to send the number from the buyer, via the Internet, to the merchant. 

Often, Ke = that is, the encryption and decryption keys are identical, and in this case we refer to it simply as the key or the secret key. This is called symmetric or secret key cryptography. In contrast, in asymmetric or public key cryptography, the encryption keys and decryption keys are different from each other, and only the decryption key needs to be kept secret. In public key cryptography, the decryption key is also sometimes called the secret key. 

The concept of public key cryptography was originally proposed in 1976 by Whitfield Diffie and Martin Heilman, and independently by Ralph Merkle. In 1997, Britain s Government Communications Headquarters (GCHQ) released previously classified documents revealing three British government employees, James Ellis, Clifford Cocks, and Malcolm Williamson, developed these same ideas several years earlier, but kept them secret for reasons of national security. There is some evidence that the United States National Security Agency (NSA)... 

With public key cryptography, some of the key management problems are solved. However, in order for Alice s public key to be useful, it is important that others know that it is her key, and not someone else masquerading as her for the purpose of receiving her secret messages. Hence, it is important that the binding between a public key and an identity is authenticated. Wide-scale methods for doing this are called public key infrastructures, and are also described below. 

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