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# Maths help - Modular Functions

Trying to get an RSA algorithm to work but getting stuck where mod is brought in.

If I have the equation

7x = 1 (mod 20)

x = 3 as 21/20 gives a remainder of 1 (this is on an example online)

But I dont understand what is actually happening & my encryption always ends up the same as the number I try to encrypt so the algorithm doesnt work when I try to use my own numbers.

Wikipedia suggests using the Extended Euclidean Algorithm but I dont really understand it.

I'm doing a research qualification & choose to do it on how credit card transactions are secured. But only having AS level maths up to now & it being a project you arent taught where I have to learn & research it all I am struggling.

Any help or advice would be appreciated.

Cheers
james

Give up, go out, get drunk....look at it in the morning :thumbsup:

StevenA2000_uk;5723271

Give up, go out, get drunk....look at it in the morning :thumbsup:

:giggle:

Boogie83e;5723415

]A very simple example of RSA encryption :geek:

:?

:lazy:

starsparkle2311;5723442

trust you, words of wisdom, indeed, you thicko:whistling:

Hey, Sir Isaac Newton got smacked on the napper with an apple before he founded Gravity......somethings just come to you without going looking for it.....

StevenA2000_uk;5723485

Hey, Sir Isaac Newton got smacked on the napper with an apple before he … Hey, Sir Isaac Newton got smacked on the napper with an apple before he founded Gravity......somethings just come to you without going looking for it.....

Like STDs :-D

choc1969;5723515

Like STDs :-D

STD? Isnt that telephone lines? Subscriber Trunc Dialing? :?

starsparkle2311;5723546

there's a trunk subscription? number please?:)

*69 :whistling:

starsparkle2311;5723546

there's a trunk subscription? number please?:)

You already got it ;-) Freephone 0800-STEVIE-BOY :w00t:

I should know this because I have a maths degree but I'v simply forgot!