Encryption/decryption

Originally posted by Taz2122
He claims that encryption doesn't really work since the one (or they) who came up with the specific encryption standard would know how to decipher it since they programmed it.

I'll give you a simple 1 bit encryption example using the "square root" function that you can show your friend.

The square of +3 is 9.
The square root of 9 is 3.
BUT
the the square of -3 is also 9.
Both negative 3 and positive 3 give the same answer = 9.

So now, imagine an encrypted file, containing one byte. This byte is "9".
The question is... what is the UNencrypted number?

So if you had to "decrypt" the number 9 to gain access to the secret files, you still have (by trial and error) to try both negative 3 and positive 3.

Sure, thats only a simple 1-bit encryption, but even though I've told you how it works, and even if you tell your friend how it works, neither of you can still instantly solve it.

Imagine now a more complex version of this, with 128 different examples of the above "lock" for you to try.

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Note of course that this is a hideously simplistic example, but hopefully it illustrates the point that knowing how the encrption system works doesnt just give the programmer instant access to the decrypted code.

Originally posted by Taz2122
He claims that encryption doesn't really work since the one (or they) who came up with the specific encryption standard would know how to decipher it since they programmed it.

Second example.

X multiplied by Y = Z.
This specific encryption standard sounds simple enough, but...

Consider the two prime numbers 7901 and 7919 (prime numbers are ones that you can divide by no other numbers than one and themselves). Suppose you multiply them together to get 62568019. That's a pretty simple operation anyone can do in two seconds flat with a calculator.
But what if I give you the number 62568019 and tell you to figure out the two numbers I multiplied together to make that number. You'd be there all day!

www.explainthatstuff.com...

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Note of course that this is a hideously simplistic example, but hopefully it illustrates the point that knowing how the encrption system works doesnt just give the programmer instant access to the decrypted code.

Originally posted by Spiramirabilis
reply to post by Pilgrum

 

what I was initially wondering was - is this something that can be used for more nefarious purposes? Trojan horses - key-loggers? Having been on the receiving end of this sort of thing - and not really understanding how all this works - I was reading through the thread and several people mentioned creating backdoors - kinda got me thinking

Simple still 'Stegano'd'' pictures are generally safe because you need the appropriate software running to process it to extract the embedded data. But let's suppose that software is quietly installed via a trojan attached to some 'free software offer' or irc exploit etc and auto-executing (silently) whenever you open a jpg or bmp file - any sort of malware could be delivered to you in pictures of funny cats or whatever and installed/executed when you open that picture without your knowledge (could be a virus or keylogger or anything at all). There's a never-ending supply of creative (but misguided) individuals out there working on such ways of disrupting the online society.

Re-sizing the pic or changing the format of it would effectively squash any hidden payload but don't get paranoid about it, just keep your AV software up to date and do regular backups plus remain cautious about what you download.

reply to post by Pilgrum

I have a Mac :-)

and, as everybody knows...we are completely invulnerable

many of the happy, chirpy Mac creatures living inside Appleland will tell - and have told me:

don't worry you're fluffy little head about any of this - nothing bad can ever happen on a mac :-)

thanks again Pilgrum

will someone please try to decrypt this?


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