Cryptography2008

Cryptography2008 - Issues in Cryptography and Encryption...

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Unformatted text preview: Issues in Cryptography and Encryption Spam news User authentication: Passwords Of course my password is my pets name. User authentication: Passwords Its name is Q47pY!3 I change it every 90 days Cryptography The art or science of secret writing, and of storing information in a form which allows it to be revealed to those you wish to see it yet hides it from all others. Historical Ciphers Caesar cipher (50 BC): letter = letter + 3 (rot 3) ilvk DEFGH I J KL MNOPQRSTU V WXYZABC ABCDE F G HI JKLMNOPQR S TUVWXYZ ? Historical Ciphers Caesar cipher (50 BC): letter = letter + 3 (rot 3) ilvk DEFGH I J K L MNOPQRSTU V WXYZABC ABCDE F G H I JKLMNOPQR S TUVWXYZ fish Historical Ciphers rot13: Add 13/swap alphabet halves Applying it twice restores original text ohyy-fuvg ABCDE F G H I JKLMN O PQRST U V WX Y Z NOPQR S T U VWXYZA B CDEFG H I J K L M Usenet convention used to hide possibly offensive jokes What was DES ? An acronym for the Data Encryption Standard, which describes the data encryption algorithm (DEA) DEA is an improvement of the algorithm Lucifer developed by IBM in the early 1970s. DES has been extensively studied since its publication and is the most well-known and widely used cryptosystem in the world . The DEA is a symmetric cryptosystem What is DSA? Digital Signature Algorithm ( DSA ) (together with the Digital Signature Standard (DSS)), are part of the U.S. government's Capstone project DSA is based on the discrete logarithm problem In DSA, signature generation is faster than signature verification, whereas with the RSA algorithm, signature verification is very much faster than signature generation. There are two kinds of cryptosystems: symmetric and asymmetric . Symmetric cryptosystems use the same key (the secret key) to encrypt and decrypt a message ( DES was an instance of a symmetric cryptosystem ) Asymmetric cryptosystems use one key (the public key) to encrypt a message and a different key (the private key) to decrypt it. (The most widely-known instance of an asymmetric key cryptosystem is PGP ("Pretty Good Privacy" )) . Ciphers Stream Ciphers: encrypt continuous streams of data Block ciphers encrypt block of data of fixed size Secure Shell (SSH) n 1995, Tatu Ylnen, a researcher at Helsinki University of Technology, Finland, designed the first version of the protocol (now called SSH-1 ) prompted by a password-sniffing attack at his university network. The goal of SSH was to replace the earlier rlogin, TELNET and rsh protocols, which did not provide strong authentication or guarantee confidentiality....
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This note was uploaded on 05/12/2008 for the course EPP 19601 taught by Professor Morel during the Spring '08 term at Carnegie Mellon.

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Cryptography2008 - Issues in Cryptography and Encryption...

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