Introduction and motivation We live in time of computers and scientific and technological progress but this time is also marked with many attacks on big Internet companies. So with expand of Internet people start to protect information that they exchange through Internet. In the Internet world it is necessary for systems as Internet banking, Internet shopping or e-commerce to secure private information that are transferred via Internet. This necessity leads to design security improvements of existing protocols and to design and implement cryptographic algorithms (for example protocols as L2TP, Microsoft PPTP, IPSec, SSH or algorithms as DES, Blowfish and others). Consider that we have two banks, bank "Alice" and bank "Bob" and these two banks for business purposes need the private cipher for their communication. They need this cipher to do secret bank operation. So they need the secure way, how to arrange the cip
Introduction and motivation We live in time of computers and scientific and technological progress but this time is also marked with many attacks on big Internet companies. So with expand of Internet people start to protect information that they exchange through Internet. In the Internet world it is necessary for systems as Internet banking, Internet shopping or e-commerce to secure private information that are transferred via Internet. This necessity leads to design security improvements of existing protocols and to design and implement cryptographic algorithms (for example protocols as L2TP, Microsoft PPTP, IPSec, SSH or algorithms as DES, Blowfish and others). Consider that we have two banks, bank "Alice" and bank "Bob" and these two banks for business purposes need the private cipher for their communication. They need this cipher to do secret bank operation. So they need the secure way, how to arrange the cip
Assume that several people wish to have a meeting. For this to happen, they usually have to meet somewhere. If they cannot meet physically, then they can take part in a video (or audio) conference to discuss whatever needs to be discussed. But what if their meeting is meant to be private? In this case they need a cryptographic protocol that allows them to exchange their ideas remotely, while keeping them secure from any potential eavesdropper. In this paper we list all the necessary requirements that a cryptographic protocol must have in order to allow several persons to exchange their ideas securely over the Internet. Moreover, and based on the standard taxonomy of cryptographic protocols, we suggest several approaches on how to design cryptographic protocols that enable us to achieve our aim. Finally, we propose the design of a protocol that solves our problem.
Communication over the Internet is an integral part of the connected world. As the Internet is a public network, the data packets exchanged by the communicating parties pass through various insecure channels and untrusted servers before they reach their destinations. Still, we feel it is safe to send e-mails, visit social media websites, watch movies of our own preferences online, and shop online using credit cards. Cryptography or encryption makes it possible to protect our private information in the presence of third parties. When we browse a secured website, we see a lock symbol on the browser; it means our communication with the website is encrypted, and hence, no third party will be able to read the data packets exchanged between the browser and the website. Hypertext Transfer Protocol Secure (HTTPS) is used to establish an encrypted, hence secured communication channel between a web browser and a website. The browser website is just one example; cryptography is happening in your mobile phones, smart cards, IoT devices, and in almost all connected devices.
The practical implementation of quantum information technologies requires, for the most part, highly advanced and currently experimental procedures. One exception is quantum cryptography, or quantum key distribution, which has been successfully demonstrated in many laboratories and has reached an advanced level of development. It will probably become the first commercial application of quantum information. In quantum key distribution, Alice and Bob exploit a quantum channel to create a secret shared key comprising a random string of binary digits. This key can then be used to protect a subsequent communication between them. The principal idea is that the secrecy of the key distribution is ensured by the laws of quantum physics. Proving security for practical communication systems is a challenging problem and requires techniques that are beyond the scope of this book. At a fundamental level, however, the ideas are simple and may readily be understood with the knowledge we have already acquired. Quantum cryptography is the latest idea in the long history of secure (and not so secure) communications and, if it is to develop, it will have to compete with existing technologies. For this reason we begin with a brief survey of the history and current state of the art in secure communications before turning to the possibilities offered by quantum communications. The history of cryptography is a long and fascinating one. As a consequence of the success or, more spectacularly, the failure of ciphers, wars have been fought, battles decided, kingdoms won, and heads lost. In the information age, ciphers and cryptosystems have become part of everyday life; we use them to protect our computers, to shop over the Internet, and to access our money via an ATM (automated teller machine). One of the oldest and simplest of all ciphers is the transposition or Caesarean cipher (attributed to Julius Caesar), in which the letters are shifted by a known (and secret) number of places in the alphabet. If the shift is 1, for example, then A is enciphered as B, B→C, · · ·, Y→Z, Z→A. A shift of five places leads us to make the replacements A→F, B→G, · · ·, Y→D, Z→E.
What does it mean for a cryptographic protocol to be "secure"? Capturing the security requirements of cryptographic tasks in a meaningful way is a slippery business: On the one hand, we want security criteria that prevent "all potential attacks" against a protocol; on the other hand, we want our criteria not to be overly restrictive and accept "reasonable protocols". One of the main reasons for flaws is the often unexpected interactions among different protocol instances that run alongside each other in a composite system.This tutorial studies a general methodology for defining security of cryptographic protocols. The methodology, often dubbed the "trusted party paradigm", allows for defining the security requirements of a large variety of cryptographic tasks in a unified and natural way. We first review more basic formulations that capture security in isolation from other protocol instances. Next we address the security problems associated with protocol composition, and review formulations that guarantee security even in composite systems.
While advances in quantum computing promise new opportunities for scientific advancement (e.g., material science and machine learning), many people are not aware that they also threaten the widely deployed cryptographic algorithms that are the foundation of today's digital security and privacy. From mobile communications to online banking to personal data privacy, literally billions of Internet users rely on cryptography every day to ensure that private communications and data stay private. Indeed, the emergence and growth of the public Internet and electronic commerce was arguably enabled by the invention of public-key cryptography. The key advantage offered by public-key cryptography is that it allows two parties who have never communicated previously to nevertheless establish a secure, private, communication channel over a non-private network (e.g., the Internet). Recent advances in quantum computing signal that we are on the cusp of our next cryptographic algorithm transition, and this transition to post-quantum cryptography will be more complicated and impact many more systems and stakeholders, than any of the prior migrations. This transition represents a major disruption within the IT industry and will broadly impact nearly every domain of our digital lives, from global commerce to social media to government and more. Cryptographic algorithm transitions take time and involve an extensive coordination effort across many stakeholders who are involved in building and operating the world's compute infrastructure. By preparing now for the upcoming transition to these new algorithms, we can ensure a more orderly, less costly, and minimally disruptive changeover.