Today the Internet is used more and more as a transportation for information. Much of the information is confidential and should not be read by those not privileged. To protect the information from unauthorized access Cryptography can be applied. The Cryptography algorithms in use today all have their pros and cons. They are therefore suited for different applications.

Today the Internet is used more and more as a transportation for information. Much of the information is confidential and should not be read by those not privileged. To protect the information from unauthorized access Cryptography can be applied. The Cryptography algorithms in use today all have their pros and cons. They are therefore suited for different applications.

The use of insecure networks -such as the Internet- to send and receive information has made the need for preventing unauthorised people reading it yet more important. One of the easiest way to do this is through public key Cryptography. However, the problem with this solution is how to tie a specific public key to a certain subject. This is solved by letting a trusted third party issue a certificate that holds, as a minimum, the name of the subject and the subject's public key along with the issuer's digital signature on the information. The rules we make for issuing, revoking and verifying of certificates and the entities that are being used to do so are called PKI - Public Key Infrastructure.

Chinese Remainder Theorem is used to solving problems in computing, coding and Cryptography. In computing we can compute with shorter numbers instead of large numbers and this will make the computing-process faster and easier. In coding it can be used for error-searching and error-regulating.Cryptography means that we can send a coded message and that no one will be able to read it without the decode-key which is based on prim-numbers. I am writing about the history of mathematics and how the number- and decimal number-system is used in Babylon, Egypt, Greece and in China. Abacus was a very important aid to calculate advanced mathematical problems.

This work is about Cryptography in general but also how the encryption works, and what's needed for encryption to work. I will also take up a little around the history around the encryption..

Detta arbete är ett examensarbete i matematik på kandidatnivå vid Växjö universitet. Det är en studie av kodningsteori i allmänhet med fokusering på cykliska koder och Reed-Solomon-koder i synnerhet. Reed-Solomon-koderna används för att skapa McElieces kryptosystem. En kortfattad analys av McElieces kryptosystems säkerhet görs tillsammans med en genomgång av kända sätt att forcera denna typ av kryptosystem. Här visar det sig att användning av Reed-Solomon-kod försvagar kryptosystemet i förhållande till om den ursprungligt föreslagna Goppa-koden används.

Communication is a part of everyday life. The more sensitive information we handle, the more interesting the question around security of your information becomes. There are two ways of handling security around the information you want to communicate, either you control the means by which you are communicating. Or you control the way you communicate, making you able to use existing communication channels. Existing methods within Cryptography enables two parties to communicate information securely.

This master?s thesis investigates the technology and security awareness associated with wireless networks (WLAN). It has been stated by the media and theories that many wireless networks are unprotected. This has sparked an interest to investigate the phenomenon in the Jonkoping region. The study is based on the following research questions:- What security weaknesses are present with the WLAN-technology and how can these be avoided?- How does the wireless infrastructure in the Jonkoping region look like?- Why do companies implement the WLAN-technology?- Are the companies aware of the risks involved with WLAN?We conducted this study in three steps; the first step was to hack a wireless network in a controlled environment in order to investigate the weaknesses of the commonly used security measures.