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CryptologyCryptologyCryptologyCryptologyTim CahillTim Cahill
Ryan ChurchRyan Church
Cryptology• Cryptology - the science and study of cryptanalysis and
cryptography.
• Cryptography - the procedures, processes, methods, etc., of making and using secret writing, as codes or ciphers.
Ex: The process where you take your message and encode it using a key you make up. your sentence = yana is awesome your key = +3Encoded message = bdqd lv dzhvrph
• Cryptanalysis - the procedures, processes, methods, etc., used to translate or interpret secret writings, as codes and ciphers, for which the key is unknown.
Ex: encrypted segment = DEF cryptanalysis is the process where you go from the encrypted segment “DEF” to the decrypted segment “ABC” without using the key.
Terms (cont.)• Public key = in cryptography, a
value associated with a particular person and used to decrypt messages from that person or encrypt messages to him/her.
• Ex: key can be anything you make up, it could be as simple as encryption = letter +3, or more complicated like encryption = letter +3 -2 *3 /2.
• PROJECT PROGRESS• Main project is a hill cipher.
Which is a more complicated cipher which involves a two by two matrix.
Programming Example• Caesar cipher:
• #include<stdio.h>#define SIZE 10int main(){ int i=0; char z, x[SIZE], c[SIZE]={0}; printf("Enter a 10 character message: ");
while(i<10){ c[i]=getchar(); i++; } i=0;
while(i<10){ x[i]=c[i]+3; printf("%c", x[i]); i++; }
printf("\n\n"); i=0;
while(i<10){ z=x[i]-3; i++; printf("%c", z); } printf("\n");
return 0;}
Quiz• 1) What is the difference between cryptology and
cryptography?
• 2) What is the main use for cryptology?
• 3) Draw how public key is used.
• 4) What would the encoded message of Yana be if the key is +4?
References• Spam and the ongoing battle for the inbox.
Communications of the ACM, Volume 50, #2 (2007), pages 24-33.Joshua Goodman, Gordon V. Cormack, David Heckerman.
• Textbook: Invitation to computer science java versionEdition 3, Schneider, copyright 07. pages 600-607
• An overview of cryptography. Gary C. Kessler, may 1998 (23 January 2009). (website) www.garykessler.net/library/crypto.html#purpose
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