an overview of cryptography ying wang-suorsa helsinki university of technology
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An Overview of Cryptography
Ying Wang-SuorsaHelsinki University of Technology
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Objectives
To provide you with an introduction to cryptology Some terms and concepts behind basic
cryptographic methods Some basic cryptographic algorithms Trust models
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Cryptography : the art of providing securecommunication over insecure channels.Encode text and provide a method for decodingNot hide message!
Confidentiality : Ensuring that no one can readthe message except intended receiver.Authentication : The process of proving one'sidentity.Integrity : Ensuring the received messages has notbeen altered in any way from the original.Non-repudiation : A mechanism to prove that thesender really sent this message.
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Levels of CryptographicAction – In today's internet, most Syst. are split between application level and transport level.
7 – Application
6 – Presentation
5 – Session S-HTTP
4 – Transport SSL
3 – Network IPSEC
2 – Data Link PPTP
1 – Physical
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Importance of Cryptography
Military applications : command and controlDiplomatic applications : information gathering, spyEconomic applications : Information protectionBanking transactionAuthentication and signaturesModern e-commerce
How can the public use cryptography quickly and safely?
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Importance of Cryptography
Modern methods of communication are inherentlyinsecure
Internet is very insecure Ethernet networks liable to having sniffers Cable modems pass through other people's homes
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Pre-computerized Crypto schemes
Transposition Ciphers Reverse pairs of lettersHELLO WORLDEHLL OOWLRD Remover every second letter and put it at the endHELLO WORLDHLOWRDEL OL Reverse the lettersHELLO WORLDDLROW OLLEH Many trickers...
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Pre-computerized Crypto schemes
Substitution Ciphers
ABCDEFGHIJKLMNOPQRSTUVWXYZBADCFEHGJILKNMPORQTSVUXWZY
HELLO WORLD GFKKPXPQKC
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Types of Cryptographic Algorithms
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Why Three Encryption Techniques?
The answer lies in that each scheme is optimized for some specific applications
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Trust Models
PGP Web of Trust
Kerberos
Public Key Certificates and CertificateAuthorities
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Kerberos Architecture