These authentication systems can also provide, when required, confidentiality (using encryption) when transferring data over insecure networks. 4. Cryptography Cryptographic mechanisms are widely used for authentication in today's networks. There are two basic types of cryptography (symmetrical and asymmetrical). One of the fundamental problems for cryptography is to transport secret keys.
4.1. Symmetric Cryptography Symmetric Cryptography includes all systems that use the same key for encryption and decryption. So Thus, if someone gets a key, he can decrypt and read the information encrypted with it. Such a person will be able to encrypt and send any data, passing them off as the information sent to a legal owner of the secret key. This means that the knowledge of key undesirable third party fully compromises the confidentiality of the system.
Consequently, the used keys should be delivered safely, either by courier, or using a special transfer protocol keys, the best of which is the algorithm of Needham-Schroeder NS78, NS87. Widely used algorithm is des (Data Encryption Standard), which has been standardized for the protection of government information in usa. He is one of the best symmetric encryption algorithms NBS77. Well-known system, operating on open networks, is the authentication system is Kerberos (TM), which was developed as part of Project Athena at mit SNS88, BM91, KN93. Kerberos is based on the des algorithm and uses a special server that stores the secret keys of all users and services. It can generate codes that allow users and processes to identify themselves other systems.
A team of designers in the print shop throws up his hands and said that the layout in order to bring longer and more expensive than the mark up again. Similar problems do not occur only rarely print publishers. Further details can be found at PCRM, an internet resource. Even highly qualified people who know the whole publishing process, not immune to the banal lack of fonts. Further, should make a small digression. The consequence of such problems is to create two different sets of fonts: TrueType (for office systems) and Type1 – for printing. If you look in terms of a simple user is no difference between them: Select the text you selected in the font name sent a document to the printer and ready. But here's the processes occurring between text editor and printer in each case differ dramatically, so often with commercial printers, paper, typed fonts, TrueType, will not work. And even cross-platform PDF-file will not help here: Inscription TrueType just porushat entire document.
It seems there is no problem, sort of like enough to buy and install Type1 and sleep peacefully. But the problem is that these fonts were written for the printing and publishing, so their sets are quite expensive. and what to do those small businesses and just private entrepreneurs, who are unable to afford to pay for makeup, and print a leaflet is needed? What do newcomers tipografnom case study the function 'Create a brochure' in ms Word, but have no ability or desire to understand the subtleties of prepress? A good option is to use a virtual printer. It allows you to finally merge the two realities in one. It's simple: you 'print' laid out a brochure on the virtual printer and get a result file which exactly shows all the artwork. Even the pdf, resulting in such a way that 'understands' Fonts TrueType, since the document is saved in it bitmap, whose parameters can be set so that the print quality will not differ from that obtained in the traditional way. No matter what the hidden subtleties prepress you do not taken into account – your brochure will look like you wanted.