My Math Forum a multiplicative cipher
 User Name Remember Me? Password

 Number Theory Number Theory Math Forum

 May 26th, 2012, 01:08 PM #1 Member   Joined: Mar 2012 Posts: 32 Thanks: 0 a multiplicative cipher [Moderator note: question was deleted by user; see the now-restored third post.]
 May 26th, 2012, 04:10 PM #2 Math Team   Joined: Apr 2012 Posts: 1,579 Thanks: 22 Re: a multiplicative cipher Lots isn't clear here. Since you are using z26, I assume you are associating every letter of the alphabet with a number between 0 and 25 inclusive. Is that correct? If so, do you start with 0 or 1 (or some other number, for that matter)? It'll make a difference. If w=23, it looks like the answers to my questions are yes and 1. If so and 'multiplicative' means you multiply the numerical values of the letters together, then 'when' = 23*8*5*14 mod 26 and I'm getting 16. I'm too tired to recheck my arithmetic. If this is the way this is supposed to work, this an odd cipher, since many different numbers can multiply out to the same number, especially in modular arithmetic, and decrypting even if you know the key is therefore not just difficult but impossible, as information is irretrievably lost.
 May 27th, 2012, 02:51 PM #3 Member   Joined: Mar 2012 Posts: 32 Thanks: 0 Re: a multiplicative cipher A multiplicative cipher is defined on Z26 by the rule M5(m) = 5×26 m. Messages in English are coded numerically using the correspondence below. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 (i) Encipher the message ‘Who’ using M5 (that is, find the ciphertext for this message). i just need to get a little start off with the w.. i got w=15 when i worked this out as i got my multiplicatice inverse of 5 in z26 to be 21 is this correct
May 27th, 2012, 06:11 PM   #4
Math Team

Joined: Apr 2012

Posts: 1,579
Thanks: 22

Re: a multiplicative cipher

Quote:
 Originally Posted by milly2012 A multiplicative cipher is defined on Z26 by the rule M5(m) = 5×26 m. Messages in English are coded numerically using the correspondence below. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 (i) Encipher the message ‘Who’ using M5 (that is, find the ciphertext for this message). i just need to get a little start off with the w.. i got w=15 when i worked this out as i got my multiplicatice inverse of 5 in z26 to be 21 is this correct
21 = -5 mod 26
5*-5 = -25 = 1 mod 26
Yes, 21 is the multiplicative inverse of 5 mod 26

w = 23 in this system. 23 = -3 and -3*-5 = 15 mod 26

So, if you are taking the numbers initially assigned value and multiplying it by the multiplicative inverse of 5 mod 26, you are right.

 May 28th, 2012, 01:07 AM #5 Member   Joined: Mar 2012 Posts: 32 Thanks: 0 Re: a multiplicative cipher Thanks johnr
 May 28th, 2012, 03:54 AM #6 Newbie     Joined: May 2012 From: Surrey, UK Posts: 6 Thanks: 0 Re: a multiplicative cipher So does this mean that H = 8 = 17 (mod26) ?
 May 28th, 2012, 04:36 AM #7 Global Moderator     Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,885 Thanks: 1088 Math Focus: Elementary mathematics and beyond Re: a multiplicative cipher The account for milly2012 has been deactivated.
 May 28th, 2012, 05:17 AM #8 Newbie     Joined: May 2012 From: Surrey, UK Posts: 6 Thanks: 0 Re: a multiplicative cipher Hmmm. No that's not right. Certainly. Could you clear up how to go about this, please. You don't necessarily have to use the letters above, but a swift run through any of them would set me at rest. Thank you.

 Tags cipher, multiplicative

Search tags for this page
,

# mathematics assignment number theory ciphering questions

Click on a term to search for related topics.
 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post threesixtify Applied Math 0 January 22nd, 2013 05:53 AM rayman Abstract Algebra 2 October 9th, 2012 10:57 AM purecotton Number Theory 1 May 28th, 2012 07:30 AM TheSwede Advanced Statistics 2 August 1st, 2011 11:25 PM nooblet Number Theory 3 March 12th, 2009 04:46 AM

 Contact - Home - Forums - Cryptocurrency Forum - Top

Copyright © 2018 My Math Forum. All rights reserved.