Intro to Encryption 244
An anonymous reader submitted a Techworld story which is a sort of encryption primer. The difference between codes & cyphers, and what all those acronyms like RSA and DES actually mean. This is good primer material for newbs, and a good refresher for fogeys.
Inaccuracy in article? (Score:5, Informative)
Certificates are 1024 or 2048 bit with SSL. On the other hand, once the key is sent and shared, a 128 bit symmetric form of encryption is used. The only thing RSA is used for is sending / receiving the symmetric encryption key, yes?
Correct me if I'm wrong.
Much better than that article (Score:5, Informative)
Intro to Colour Contrast (Score:0, Informative)
Handbook (Score:5, Informative)
Re:intro to encryption (Score:5, Informative)
n o p q r s t u v w x y z a b c d e f g h i j k l m
first post!
Applied Cryptography (Score:5, Informative)
It comes with source too! You know you love source....
Not really the best intro for crypto (Score:5, Informative)
Clarification on web-browser security... (Score:4, Informative)
>> so cannot be considered secure against a determined
>> and sufficiently well-resourced attack.
The 128-bit there is the symmetric cipher key length, RSA is
used for signature authentication and not encryption, key
exchanges occur via hand-shake algorithms ie: diffie-hellman
and derivatives there of...
a 128-bit symmetric cipher is actually very strong, for temporary
transit data ie: purchase data, cc numbers etc.
Arash Partow
_________________________________________
Be one who knows what they don't know,
Instead of being one who knows not what they don't know,
Thinking they know everything about all things.
http://www.partow.net
Re:Handbook (Score:2, Informative)
Re:Inaccuracy in article? (Score:3, Informative)
Re:Inaccuracy in article? (Score:5, Informative)
Kinda yes. The public key is used to encrypt the session key, which is used in turn to encrypt the payload using a symmetric algorithm for speed.
Certificates are a bit bigger than 1024 or 2048 bits. They contain the public key (consisting in the case of RSA, among other things, of the 1024/2048 bit modulus) the owner's identification (e.g. e-mail address, common name, url,
A certificate is just that; it's to certify that a certain public key belongs to a certain entity.
If you pay enough to microsoft/opera/etc., you can certify anybody you want and all internet explorer users will take it for granted, because no one checks certificates.
Re:Inaccuracy in article? (Score:2, Informative)
I don't understand your point here...
Digital signatures most definately have to do with encryption, otherwise they could be forged, trivially. Absolutely any public-key crypto-system should be able to be used as the main part of a digital signature system.
Perhaps I misunderstand what you are trying to say.
random & pseudorandom pads (Score:5, Informative)
That said, paddign with pseudo-random data is very unsafe. Breaking this type of encryption is typically one of the first homework assignments in cryptography courses. The article is either very fuzzy on this distinction, or plain out wrong, depending on how you read it.
Re:Handbook (Score:5, Informative)
Not only does it cover the same ground, it also goes into detail a bit more about real tricky business; protocols (where most mistakes are made these days, since nearly everybody uses off-the-shelf algorithms like AES, DSA, RSA and ElGamal). This guy knows how to write, and succeeds in warning you of potential pitfalls in a humorous manner. Also, he knows his stuff; he submitted one of the AES candidates, Blowfish.
Bruce also publishes the most excellent Crypto-Gram [counterpane.com] newsletter.
Beware of not heeding Bruce's stern words of warning. You may end up in the doghouse [google.nl]! The humiliation! The shame upon your house!
Re:Comprehensive list of unsolved codes and cipher (Score:5, Informative)
The problem with challenges like "crack this uncracked cipher" is that the challenge is not realistic.
Most of these codes/ciphers give you no idea the process behind how they were generated. That's unrealistic: usually an analyst will have the algorithm that does the encryption (if not the key itself), either via open-source, reverse engineering of a public binary, legitimate purchase, or espionage.
Most of these challenges only give you a tiny piece of ciphertext. That's not realistic: if you're trying to break, say, SSL, you'll be able to get your hands on megabytes of transcripts, and you'll even be able to generate ciphertexts that correspond to plaintexts of your choice.
Most of these "ciphers" don't generalize to arbitrary messages. That's unrealistic. Sure, someone can design some ad-hoc cipher to encrypt the location of his buried treasure using landmarks, clever puns, and weird symbols. That's a far cry from being able to efficiently encrypt an arbitrary TCP/IP stream.
Re:Inaccuracy in article? (Score:3, Informative)
Many assymmetric encryption schemes only use public/private key pairs to establish a secure connection. Once a secure connection has been established, most schemes generate a private key that will be used for symmetric encryption.
The reasons for switching to symmetric are many, but primarily it is done for speed. Symetric encryption algorithms are very fast compared to assymetric. Also, symertic algorithms can easily be implemented in hardware, thus, speed boosts are even greater when switched to symetric algorithms.
This kind of answers your question, but there are still a few crazy zealots out there that insist upon the sole use of assymetric algorithms - it is more secure, but worlds slower.
Mel & Baker a good crypto book (Score:3, Informative)
Cryptography Decrypted [amazon.com] by H. X. Mel and Doris Baker is a good intro to crypto. I found it entertaining and the topics went from elementary to, uh, more than I cared to know. The appendices explaining the mathematics of crypto were interesting as well.
Re:Inaccuracy in article? (Score:3, Informative)
One other standardized signature is DSA, which is based on the hardness of computing discrete logs. The DSA algorithm itself is not the inverse of any secure encryption scheme. (It's worth noting that there are some encryption schemes based on discrete log; they're just not the inverse of DSA.)
some things newbs should learn about encryption (Score:3, Informative)
A better introduction (Score:3, Informative)
It talks about the origins of crypto a little, and leads into public key encryption, a field I have been trying to learn a little more about. Much better article than the parent!
Re:I realized something while reading the article. (Score:3, Informative)
Actually its not. There is an efficient algorithm out there for factoring numbers into primes. The only problem is that it requires technology (quantum computers) which doesn't exist yet, but which is on the horizon.
"And why is my article modded flamebait?!"
Because mods are jackasses.
Re:SETI noise (Score:2, Informative)
Re:Someone has been reading too much Cryptonomicon (Score:2, Informative)
Won't supply a link here, but Simon Singh's excellent "The Code Book" provides a large level of detail about the Polish contributions to breaking Enigma.
Ahh, what the hell, I _will_ supply a link here [armyradio.com]. Or, just google "Rejewski Enigma".
Re: Credability = Zero (Score:3, Informative)
Firstly, directly comparing symetric and asymetric key lengths shows that the authour has no knowledge of encryption. They are not directly comparable since they are used in different ways and have different meanings.
Secondly, claiming 128-bit keys are insecure shows that the authour has no knowledge of encryption. 80-bit keys are widely considered infeasible to break.
Encryption Primer (Score:1, Informative)
Re:I realized something while reading the article. (Score:3, Informative)
Correction: No-one has ever admitted to having broken PGP or GPG. Unless you know something those of us outside the NSA don't, you can never be so sure.
Remember, the Nazi's thought no-one had broken Enigma...
Re:Inaccuracy in article? (Score:2, Informative)
Unfortunately, nothing in life is free, and so it is with asymmetric cryptosystems. Since d can be computed from e given p and q, and p and q are the factors of N, they must be chosen so large that N cannot be factorised in any reasonable time.
While this is accurate, it's the first and only mention of d, e, p, q and N. The author also never actually explains that RSA is built on the assumption that prime factorization is mathematically hard. It appears that he simply cut-and-pasted from another text without bothering to make sure that it fit with the article. I can only imagine the confusion of the poor newbies trying to make sense of this.
Re:SETI noise (Score:2, Informative)
No. If you reuse it, it's easy to break. The Rosenberges went to the electric chair because some Russian spy reused a pad.
Re:Handbook (Score:5, Informative)
He wrote it after realizing how poorly people had misunderstood his warnings in Applied Cryptography (as documented in Secrets and Lies.) I thought his warnings were plain enough, but apparently too many people just plopped in some encryption because they "needed" some, and Blowfish was printed right there in the appendix.
What p, q, e, d, and N mean (Score:4, Informative)
That's it. Now, put N and e together in a file and call it your "private key", and put N and d together and call it your "public key". To use them:
In practice RSA takes too much time, so you make yourself a random key, encrypt that using RSA, and you and your recipient communicate using a symmetric cipher.
As to why ((n^e mod N)^d mod N) = n, that's where it helps to know some math. Mathweb or Wikipedia can help you, but having a bit of background in abstract algebra will help.