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One-Time Pad Encryption With No Pad?
thepooleboy writes: "The Globe and Mail has an article about a Toronto area company that has perfected 'Unbreakable Encryption' using the Vernam Cipher." The idea is to use as a one-time pad a large number generated by equations sent with an initial (proprietary) exchange which takes place when users connect to an equipped server. Since real one-time pads' numbers are by definition random and known in advance to both sender and receiver, though, the company seems to be playing fast-and-loose with their terms.
Attempts to get around the fundamental limits of data encryption (and data compression, and a lot of other software fundamentals) remind me of all the pointless efforts to build a Perpetual Motion Machine. "Yeah, the smart guys say energy is "conserved", but anybody with any common sense can see if you just tweak this gearbox this way..."
Cryptographically secure hash functions like SHA or MD-5 are often used to convert shorter, shared numbers (the key) into a long bit stream that can be xor'ed with the file in much the same way as a one-time pad. This is done all of the time.
Let k be your key. Let b1, b2, b3 be blocks of bits. Take as many as you need to encrypt the file:
b1=SHA(key)
b2=SHA(snip(b1)+key)
b3=SHA(snip(
etc....
In fact, you can use any encryption function instead of SHA with a few tweaks.
The Germans were using a variation on this in Cryptonomicon. The idea is that given an initial seed, you can generate a "key of the day" that appears random. In this case they're using an initial seed to generate a whole one-time pad.
However, it isn't secure. If you know the algorithm, you only(!) have to search the keyspace of the initial seed.
--
E_NOSIG
no, a vernam cipher is the only form of unbreakable encryption. It happens like this: you have a stream of extremely random bits. And you have to make sure they are really really random, no pseudo random number generators. Say it's coming from a satelite up in space that measures radioactive particles(this was proposed in a paper not too long ago). Now the satellite streams these bits down to earth, so anybody can access them. Alice and Bob want to communicate securely over an insecure channel. So the agree on a series of bits to encrypt with. This can be anything from "every other bit" to a large polynomial function that says which bits to use. So every bit the function designates as an encrypted bit is used to XOR any message Alice and Bob use to communitacte. So, Alice computes bit random bit number x to encrypt bit y. She does XOR(x,y)->c and sends it to Bob. Bob also has this formula and performs the calculation to find which bit number x to use, then performs XOR(c,x)->y. The key is keeping the bit number function secret. Now, why is this secure? because anybody listening on the channel doesn't know the function(hopefully) and if your bits are truely random there is *no* way to distinguish whether any given bit can be 0 or 1. Try all the combinations for 0 or 1 in the message you want, but every permutation you want will look like the correct decryption.
- "Never let a computer tell me shit." - DelTron Zero
From the article:
Once the server is set up with E2Sec, anyone who logs on through a Web browser or Internet link will automatically be given an encrypted connection. A small 4- to 10-kilobit file, a bit like a Web cookie, is loaded into the client computer's memory. The file contains a program to generate random encryption keys, so that the keys themselves don't have to be sent over the network connection. The program is so tiny that even the low-powered processors in a cellphone can run it with ease, Mr. Kassam said.
This is really unbreakable. Unless you happen to intercept this program. Which wouldn't be that hard, and it may in fact be the same program for every client. And, they're touting this for wireless communications.
I found this next part interesting:
The client generates a series of random numbers to use as an encryption key. This is number is exchanged with the server through a secure process known only to Prescient, the server uses it to encrypt any information it sends back to the client, and then the key is destroyed and a new one is created. This process is repeated every time information is exchanged between the client and the server, making it virtually impossible for outsiders to decrypt the information.
It's a well established fact that non-open, secure processes are not secure. Cryptography is difficult, folks. The only way to even come close to proving that a particular process is secure is by exposing it to the scrutiny of the entire global community. Even then, its a case of proving that something is NOT true, which in this case involves incredibly complex mathematics that don't work for half of the proposed protocols out there; for instance, for a particular protocol to be 'provably' secure, it has to be time reversible (that is, if you apply any one step in reverse, the encryption key and cipher text each go back to their state before that step)
"We're 100-per-cent confident in our technology," Mr. Kassam said. "To give an idea of how difficult this is to crack, many organizations consider 128-bit encryption, which has a [cryptography level] of two to the power of 128, to be very secure. With e2Sec, we're talking about encryption in excess of 5,000 bits, and as much as two to the power of 10,000."
Ummmm... comparing asymmetric encryption to symmetric encryption (of which a one-time pad is a subset) with key-lengths is like comparing apples to oranges. In asymmetric encryption, your security is in your keyspace... every bit doubles the time to search the keyspace. In symmetric encryption, security is all about the keys; symmetric encryption is so easy to do that you can try millions of keys a second, as opposed to thousands or hundreds, so you HAVE to have a big keyspace. But, most symmetric encryption algorithms allow you to get it partly right; if the key is partly right, you get a partly decoded message, so the search algorithm is linear instead of exponential.
I am disrespectful to dirt! Can you see that I am serious?!
Actually a one time pad is mathematically proven to be secure. The biggest problem is that a protocol using it is much tougher to find.
A one time pad is completely random therefor you could take any message, "Bob had a car" and it could decrypt to ANY message of the same length, given the right pad. The biggest problem with a true one-time pad is that as the name implies it can only be used once, and needs to be the same size as the message its encrypting.
The best practical example of one-time pads is probably the hotline between washington and moscow. The crypto course I took explained that a very very large random one time pad was created to encode the message, and new pads are periodically created and taken by curier to each site. I believe a similar method is also used for transmitting launch codes to Nuke site.
Then again its been over a year, and my memory of the course is a little fuzzy.
Eh, except that some encryption is unbreakable. See HardEncrypt, for example.
Every once in a while I like to masturbate a new word into my vocabulary, even if I don't know what it means.
All computer programs in slot machines and such are submitted (source, *source*) to some state agency, who examine the code to make sure it has no backdoors. One enterprising examiner noriced that a certain blackjack game did not reinitialize its random seed. He copied the random number generator code to his laptop, sat in a bar with a cell phone listening to his buddy report what cards came up, and within a short time knew what to play to win.
Both went to prison, as I heard it.
Infuriate left and right