Just a quick question to help me get a better handle on things:
With public key encryption, all you need is the encryption software and you can send relatively safe messages, right? Does the recipient need encryption software also, or (as it seems to me) you send the encryption key before the message? Then what's to stop someone from sniffing or stealing the key?
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Question about encryption.
Fri, 2011-10-07 09:39
#1
Azathoth
Question about encryption.
Fri, 2011-10-07 10:01
#2
sysop
Re: Question about encryption.
Ok, to answer:
1) Yes, the other person will need software to decrypt.
2) It's not as simple as that. If you're talking about things like a public key - then by implication, you also have a private key. The worry about stealing the key is relevant for one key encryption schemes - any of the old spy movie routines for example. Two key encryption is designed to prevent that specifically. See, a public key and a private key are two very long different strings - but they are related mathematically. The public key is advertised openly to anyone you want to communicate with. The private key is kept private and secure - it never leaves your hands.
When you want to send someone a message - you first look up *their* public key, and encrypt the message with that public key. You also encrypt it with your own private key. There are various ways of combining the public key of someone else and the private key of yourself, but the concept is what's important moreso than the exact how-to. Look up PGP if you need. At that point the message cannot be decrpypted without the other person's private key and your own public key. It's much like being able to lock a box with a key that belongs to someone else.
When the other person gets the file, they can decrypt it only with your public and their private keys. This confirms a) that no one else can decrypt it along the way (since they don't have the recipient's private key), and b) that the file *actually* came from you and not from someone else (anyone else wouldn't have your private key, so the public key wouldn't work if someone else made the file).
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Fri, 2011-10-07 10:21
#3
Azathoth
Re: Question about encryption.
Perfect! That clears things up. Thanks a lot!
Sat, 2011-10-08 10:06
#4
Smokeskin
Re: Question about encryption.
Actually, the calculation needed to decrypt the message is easy if you have the private key and VERY hard if you don't.
Sat, 2011-10-08 21:25
#5
sysop
Re: Question about encryption.
Well *yes*. Anything can be broken given enough time and processing power. The only thing that generally can't is a properly used one-use pad. You're right that the more accurate way to view it is "can't be realistically broken within the capabilities of our current technological abilities" but it didn't seem as necessary to answering this particular question. Seemed like a high-level rundown, pretty shallow depth, would work for the OP. :)
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Mon, 2011-10-10 07:40
#6
Xagroth
Re: Question about encryption.
Remember that, in Eclipse Phase, there are Quantum computers able to precisely break any coding, given enough time (usually, from soem hours for not quantum-codified data to some months to quantum-codified data). So the best way to move really sensitive info wihtout fear of intercepting is by Quantum Entangled emitter/receivers and physical transport of the data.
So get a courier you thrust... or one you don't, and give the fucker some sort of "ego-disease" that will kill him if he doesn't deliver the data before the time set (that is also inferior to the time required to decode the message), and that's it ^^
Mon, 2011-10-10 15:30
#7
Smokeskin
Re: Question about encryption.
That all sounds wrong.
You can only quantum encrypt communications, there is no such thing for files. QUantum encrypted comms can't be eavesdropped on at all without it being detected. Quantum computers break normal encryption with a task time of one week.
One time pad encryption is totally secure (aside from someone stealing the pad of course).
Mon, 2011-10-10 16:19
#8
Xagroth
Re: Question about encryption.
I don't really understand why I cannot grab a copy of a wireless quantum-encrypted comm wihtout being detected... at least, for what I understood, it's like telling that I cannot eavesdrop a conversation without being noticed!
As for the Quantum-codification of a file, it's quite possible: the codification key is produced by a quantum computer, maybe even terabytes in length, and only othe quantum computer can use the key. Or at least, that's how I see it, anyway, because without that ther would be no way to assure the privacy of anything.
Because, about having computers in a faraday cage and disconected from the internet is not enough, as the US military discovered recently with their drone control computers XD.
Mon, 2011-10-10 16:32
#9
Yerameyahu
Re: Question about encryption.
Are you going to talk about the game, or what? :) In the game, it's a given that you can't intercept farcasters. The kinds of available file encryption are also given. *shrug* I agree that reality/theory-based discussions are interesting, and important for setting hard-science rules, but not after the rules are there.
Mon, 2011-10-10 17:00
#10
Xagroth
Re: Question about encryption.
Now I feel dumb, somewhere I garbled what I was thinking... Farcasters should be theoretically something that can be intercepted... like reaching the speed of light is theoretically doable XD. Anyway, I was thinking about the "normal" data transmissions, which not always are done using farcasters, those, as I understood, can be intercepted (and usually generating vapors... usually).
And yeah, now that you mention it, the corebook says that basic files cannot be encrypted using quantum computers/encryption keys... (pg 254 corebook). Kinda strange, like leaving a door intentionally open...
Mon, 2011-10-10 17:06
#11
Yerameyahu
Re: Question about encryption.
Yeah, I dunno. Hold on, though, because it sounds like you're using 'farcaster' as 'neutrino farcaster', while I'm using it to mean 'anything using a quantum farcaster'.
Mon, 2011-10-10 17:22
#12
Smokeskin
Re: Question about encryption.
Exactly. If we're sharing for example entangled photons and both measure on them, we'll be able to tell if someone "looked at" them in transit, in which case we won't send the message. If the error rate is so low that no one can have looked at them, we'll use it as a one time pad encryption key and send the message.
The message isn't actually quantum encrypted, it is really just a key distribution that is 100% sure to detect eavesdropping through quantum effects.
Reading section in EP again, they got the entanglement requirement wrong btw.
No it is not possible. I have no idea what you mean by "quantum-codification". Quantum computers don't produce magical numbers, they just produce regular numbers.
Encrypting your data with an OTP would be completely safe. Mathematical encryption on the other hand is susceptible to decryption, and quantum computers can do it within reasonable timeframes, not because they are superfast but from their abiliy to do certain mathematical operations that allow them to "cut corners" and bypass the calculations that makes normal computers take an incredibly long time. If mathematical file encryption schemes that can also choke quantum computers can be found, I don't know, but they don't seem to exist in EP.
Tue, 2011-10-11 08:15
#13
Xagroth
Re: Question about encryption.
In the most basic sense, a quantum computer can produce a private key so big and long that the required time for even another quantum computer to decode the file without the key would mean months (consider that nowadays the encryption can last for years before being broken, and we are talking about normal computers generating and trying to decode codification keys less than a few Mb in length). Of course, there are thousands of options to complicate things, with the instructions being in the key, to delay brute force hacks... things like "every third "a" is changed for a "z", and every second "e" is changed to a "w", plus the first word of any phrase is written in phonetic japanese, the second in phonetic vietnamese, the third in navajo...", and I shudder to think about the use of alien languages or invented ones.
Even with the "intuition" equivalent that gives the edge to quantum computers over normal computers, things can be made so complicated that it can take hours for the QC to decode the message with the proper decoding keys... at least, that's what I was thinking when I wrote those paragraphs.
Tue, 2011-10-11 09:26
#14
Smokeskin
Re: Question about encryption.
Quantum computers don't produce magically big (and long? and?) numbers, they just produce regular numbers.
Sure. The kind of mathematical public key encryption we talk about will only get you the text that was encrypted. If there is additional decoding to be done, then that comes next. Simply translating words to other languages should be simple enough, but it can be made very difficult (and of course a one time pad would make it totally impossible to crack).
Also, there are mathematical encryption schemes that don't seem to allow quantum computers much of an edge, people can just switch to those if they want to be safe from QCs. though in EP, it seems that mathematical breakthroughs have occured that allow QCs to break all types of public key encryption (sort of like in Shadowrun where any encryption is easily broken).
AFAIK quantum computers don't have an edge in decrypting messages with the proper decoding keys. Remember that quantum computers aren't generally faster, but there are a few special operations they can do very effectively. I don't think they apply to the standard encryption-decryption scheme.
Tue, 2011-10-11 14:22
#15
Xagroth
Re: Question about encryption.
I meant strings of numbers. Like the difference between our calculator producing pi with 10 digits (including the 3.14159) and a computer producing like a hundred or more in the same time. Anyway, the point I defend is that no matter what you make to encode something, there is always a way to break the coding... given enough time, which means (to me) anything quantum-coded could take hundreds of years to be decoded by brute force means, making it effectively impossible to decode.
Of course, one wonders about TITANS... and things on their level, regarding coding and the like.
Tue, 2011-10-11 14:50
#16
Yerameyahu
Re: Question about encryption.
You're still calling something 'quantum-coded', and I don't understand what that's intended to mean.
Tue, 2011-10-11 16:50
#17
thelabmonkey
Re: Question about encryption.
It should be noted that... http://xkcd.com/538/
:D
Tue, 2011-10-11 16:57
#18
Yerameyahu
Re: Question about encryption.
Ascalaphus did note that. :)
Wed, 2011-10-12 04:48
#19
Arenamontanus
Re: Question about encryption.
This is wrong.
See https://secure.wikimedia.org/wikipedia/en/wiki/Information_theoretic_sec... (or *any* textbook on cryptography) :
"A cryptosystem is information-theoretically secure if its security derives purely from information theory. That is, it is secure even when the adversary has unlimited computing power. An algorithm or encryption protocol that has information-theoretic security does not depend for its effectiveness on unproven assumptions about computational hardness and such an algorithm is not vulnerable to future developments in quantum computing. An example of an information-theoretically secure cryptosystem is the one-time pad."
The one time pad also achieves perfect security: "an encryption algorithm is perfectly secure if a ciphertext produced using it provides no information about the plaintext without knowledge of the key. "
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Wed, 2011-10-12 05:22
#20
Xagroth
Re: Question about encryption.
Given a concrete situation, even a one time key can be decoded, but it would be a situation almost impossible to happen in EP or nowadays, so I won't bother using it to discuss it. Anyway, I stand corrected, but I still bet a lot of corps use quantum-entangled comms for their most secure transmissions.
Wed, 2011-10-12 08:42
#21
Yerameyahu
Re: Question about encryption.
No, they use QE for their *fastest* transmissions. Like everyone else, they use (radio/laser/neutrino/whatever) farcasters if they want it to be secure… because they're unbreakable (without mentioning things like social engineering, or a thousand other external non-crypto factors). :)
Let's talk about the science again, it's fun. Who know how the farcasters work? There was an explanation earlier that seemed to say 'they're transmitting entangled photons' (which doesn't sound right), and then also said they got entanglement wrong. :/
Wed, 2011-10-12 10:02
#22
Arenamontanus
Re: Question about encryption.
I got the impression that the basic farcasters are supposed to be neutrino-based, which is cool but likely impractical according to current science (neutrinos interact with stuff via the weak force, so you need a lot of energy to get a wimpy neutrino beam, and then a lot of sensors to catch even that). But neutrinos are un-jammable, unless you can overload the detector by sending a beam at it.
A more plausible approach is laser links. A laser beam is a great information carrier, but it does require line of sight. The higher the frequency the better the bandwidth, and in space there is nothing dampening the signals except spreading over distance (and again, a large aperture comms dish and a high frequency allows you to retain focus over pretty long distances - a 400 nm laser beam with a 1 m transmitter will be just 20 km across at a 1 AU distance, and could in theory give you terabit bandwidth). Receivers can be jammed by other beams, of course.
Quantum entanglement is possible with both neutrinos and photons in lasers. Note that sending entangled particles is not QE communication, but just "vanilla" quantum encryption: you use the entangled particle pairs (one for you, one for the recipient) to exchange a key safely. Entangled neutrinos exist, although they are likely a *nightmare* to handle right.
QE comms seems to be both unjammable and impossible to listen in to (due to their quantum nature - you do something to your qubit and somehow the other qubit at the recipient does something, with non exchange of photons or any detectable particles). But... [insert obligatory rant about their FTL properties here :-) ]
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Wed, 2011-10-12 10:15
#23
Yerameyahu
Re: Question about encryption.
Yeah, so you're saying there are a couple problems. Farcasters (book) worth with any (EM/particle?) medium (radio, etc.), which isn't compatible with the science, right?
Also, my personal ignorance, how are you 'sending entangled particles'? The book claims the two farcasters are 'entangled with each other', but what's that mean w.r.t. 'sending entangled particles'? Thanks for patience. :D
I feel that I'm fully clear on QE comms, though. :) Hehe.
Wed, 2011-10-12 15:53
#24
Xagroth
Re: Question about encryption.
Mmmm... As I understood it, the Quantum Entangled bits are like mirrors one of the other: regardless of the distance between them, changing one activates a change in the other, and then they become dissociated because those two qubits lose that property. You could say it's like making a hole between a foam wall... only each sides of the wall can be anywhere. And yes, qubits are mostly used in gatecrashing operations because the FTLspeed of comms.
Then Farcasters (both implant and station) work like small supernovas that carry data somehow, so they can transmit usually with 100% success. It's like the "the character "survives" unless the GM needs otherwise and can justify it", with a death switch included for free.
And finally the cheap usual radio signals. How one can reach from the sun to the Kuiper belt without getting tons of parasites, I don't know, but I suppose there are repeaters... but that also would make it easy to eavesdrop.
Wed, 2011-10-12 16:39
#25
Smokeskin
Re: Question about encryption.
Oh please do tell me how you could decode it. I was under the clear impression that a one time pad encoded transmission contained no information at all about the cleartext, not a single bit. If I encoded "Hello" you could work on it forever and never get any closer to the cleartext than a list of all combinations possible with 5 characters, unless you got hold of the pad.
Wed, 2011-10-12 16:57
#26
Yerameyahu
Re: Question about encryption.
Xagroth, again, I think you're referring to *neutrino farcasters* when you say 'farcasters'. However, this is only one kind of farcaster communication; you can also have a farcaster using laser, radio, etc. My question is roughly, 'how do these work?'. :)
Wed, 2011-10-12 17:14
#27
Smokeskin
Re: Question about encryption.
Yeah, the book farcaster makes little sense - it is two entangled machines that let you encode any type of signal so eavesdropping is instantly detected. It makes little sense, not just because with light speed lag how do you abort?
Real quantun encryption doesn't require entangled machines (whatever that means), and you don't "quantum encode" the signal. You send a stream of photons that are one part of a quantum entangled pairs (or similar) and both measure on them. If the error rate is high, someone eavesdropped and you abort. If the error rate is low, no one listened - a listener's observation would interfere with the quantum system. With no eavesdropping you have just securely exchanged a one time pad at a distance. You then use this as a one time pad for your message thatnyou can then transmit with unbreakable encryption through any data channel, radio, laser, mesh.
Sending entangled particles is just creating an entangled pair and sending one particle to the receiver. I see some very real problems in doing this over interplanetary distances though.
Regarding the book entangled farcaster, it seems that it would just be a qubit reservoir that allows for real quantum comms - or if not, with the requirement of the two machines to be physically together and then transported apart, why not just have it contain a one time pad?
Thu, 2011-10-13 06:31
#28
Xagroth
Re: Question about encryption.
I think the game presents us quantum computers as somehow randomized, yet predictable, iterations of any data introduced in the computer. So, given two computers with exactly the same "seed" or origin, they could retrace a coded message to the uncoded state. I think it's consistent with the quantum entangled description, but only that. In essence, you could consider two coordinated quantum computers as a "one time pad" with infinite uses.
As for the decription of a one time pad-coded message, there are several requirements that is not realistic to expect to happen nowadays, much less in Eclipse Phase. Essentially, you need for the coded file to be a long text-only, and then you look for the rules for decryting a language. For example, if I recall right, the letter "e" is the most repeated one in english, and following those rules you can more or less start to decode a text. However, is a technique that, in EP, would be used almost only by archaeologists and xenoarcheologist.
Anyway, I always thought the best way to keep data safe is the steganographic technique (up to eleven XD): for example, hiding the blueprints to assemble some ilegal goods inside an RPG, requiring determinated characteristics to access it (like a concrete name for each of the player's party members, doing determinate thing in a concrete situation, etc...). In other media, we have the classic concrete edition of a book both the sender and the receiver have, with a long letter that indicates somehow what silabes to pick from where, or even images containing the data hidden (images that no one would look twice, from vacation photos, family photos... or disgusting pornographic images). Using images to transmit instructions is, in fact, one of the ways my view of the barsoomians use to transmit certain data between members, a sort of barcode using certain pigments that can be seen using infrared or ultraviolet eyes, hidden inside graffity in Valles-New Shanghai (and no, it's not as simple as a barcode printed in infra/ultra over a graffitty).
Also, I'd like to mention some details that, while are not encryption per se, can be used to keep the enemy from your comms: essentially, technology advances, so eventually there is an uncompatibility between hardware. This is about exploiting the incompatibility. In a real life example, the spanish army still has 40 or more years old radios (in fact, I think they have some Vietnam-surplus radios) that just cannot be received by modern radios (unless they change a lever in the old model XD).
Thu, 2011-10-13 07:50
#29
Smokeskin
Re: Question about encryption.
It doesn't sound like you know what a one time pad is. Maybe you're thinking of a substitution cipher?
A one time pad is a random string of bits (or chars or whatever) at least as long as the cleartext, that you encode your clear text with by using XOR - if it is a 1 you flip the bit, if it is 0 you don't. The cipher text will then also be a random string.
With one time pads, there is NO information in the cipher text about the clear text (except for message length). Literally no information. You can count chars or repeated sequences or whatever you want in the cipher text, they will be COMPLETELY unrelated to the clear text. Sorry for using caps, but I said the same before, and when you start talking about trying to find 'e's in the text, you must have missed it.
It can be used on any kind of data, it is all just bits after all.
Thu, 2011-10-13 09:40
#30
nezumi.hebereke
Re: Question about encryption.
This attack doesn't work with a one-time pad, however it is a valid attack against some other basic forms of encryption. And it is still a valid attack in a digital world. You wouldn't be looking at letters, but you would look at the hexadecimal data. Some hex characters are going to be more common in a particular piece of data than others. So for example, if you're looking at a piece of software and you have a good guess what platform it's intended to run on, say 0xA0 is the hex code for 'ADD', which is the most common command (totally making this up), then you can do frequency analysis on that, and gradually rebuild the code that way. As long as you know basically what the transmitted data is, I'm guessing this could work for most types of data.
(But again, this is an attack unique to a limited set of relatively weak encryption algorithms. It's not likely to be a common attack method in EP.)
Mon, 2011-10-17 11:58
#31
The Doctor
Re: Question about encryption.
The sender and recipient need the same (or compatible) cryptographic software. Both need to have generated keypairs (public and private), and gotten their public keys into the hands of the intended recipients in such a way that their provenance is trusted by the recipient.
The way public key cryptosystems work is that anyone can encrypt a message to someone using the recipient's public key. The recipient of the encrypted message then uses their private key to decrypt the message and extract plaintext.
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Mon, 2011-10-17 11:59
#32
The Doctor
Re: Question about encryption.
The weakest link in any security system are the system's users.
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Mon, 2011-10-17 12:02
#33
The Doctor
Re: Question about encryption.
...which unfortunately starts the [url=https://secure.wikimedia.org/wikipedia/en/wiki/Slippery_slope#The_slippe... slope[/url] argument that encryption is inherently suspicious, and everyone should just give up.
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Mon, 2011-10-17 12:13
#34
The Doctor
Re: Question about encryption.
What you describe is a character frequency attack against a cryptosystem. This is easy to thwart by compressing the data, which is pretty much standard operating procedure now, and thus would be a basic assumption in EP.
Generally speaking, when staging a cryptanalytic attack Eve throws everything and the kitchen sink at the procedure to see 0) what works, and 1) what information can be gained from failures that might provide useful clues later. Enough of the usual information gathering attacks are automated so the attacker does potentially gains much but loses little in running whatever the EP equivalent of the Cryptographer's Workbench is against a cyphertext to see what can be deduced.
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