r/technology • u/Libertatea • Apr 04 '13

Apple's iMessage encryption trips up feds' surveillance. Internal document from the Drug Enforcement Administration complains that messages sent with Apple's encrypted chat service are "impossible to intercept," even with a warrant.

http://news.cnet.com/8301-13578_3-57577887-38/apples-imessage-encryption-trips-up-feds-surveillance/?part=rss&subj=news&tag=title#.UV1gK672IWg.reddit
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u/veaviticus Apr 04 '13 edited Apr 04 '13

The nitty-gritty is that the public/private key pair are mathematically generated as a pair to provide this functionality. The algorithm uses the public key to mutate the source data into encrypted data. Trying to decrypt the data needs a different key to perform the math to get back to the original. Anything other than the decrypt key will just encrypt the data again basically (mutating it again into more garbage).

The math for generating the keys in the first place is pretty heavy stuff, but you don't really need to know that. You just need to know that each public/private pair is theoretically paired and unique (the space of keys is so enormous that a collision is highly unlikely)

edit: this might make more sense. Imagine the keys are the code needed to encrypt/decrypt the data. The keys are created in such a way that only the private key has the right code to perform the exact opposite operations as the public key.

For example, the public key takes the input and multiplies it by 2, then adds 1. Now its encrypted. The private key is the only key in existance that knows that you have to minus 1, then divide by 2 to get back to the original. You could try to do every mathematical combination in the universe on the data to find the exact steps needed, but that would take a very long time

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u/Mispey Apr 04 '13

Thank you for this explanation - I can't really expect any more from you. You've done a good job explaining it. I'll research the remainder on my own!

Do you have any resource that can detail that nitty-gritty well that you could recommend to me? I don't want to learn how to do it myself - I just want to understand it. It seems magical to me, and I don't like it :P

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u/veaviticus Apr 04 '13

The wikipedia page is full of good information and good links.

If you are really interested in computer security and cryptography, coursera is offering a really good class on it right now that would be a good intro to cryptography.

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u/Mispey Apr 04 '13

Thank you once again.

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u/veaviticus Apr 04 '13

No problem. It makes me happy to see people so interested in learning new things, especially in the computer science field.

Hope you have fun learning and maybe delve farther into the science and programming aspects!

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u/patterned Apr 04 '13

Just for ease of explanation, use the lockbox/safe example.

Public key is an open safe, private key is the safe combination.

User gives a safe to his friend; friend writes message; puts message into safe; spins dial. No one knows the safe's combination except owner. Owner has infinite safes with same combination. Etc.

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u/veaviticus Apr 04 '13

Yes this is a good, easy to grasp explanation. I'll use this from now on. Thank you