jansson_mark
Markus Jansson
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join:2001-08-05
Finland
| reply to boomerbubba
Re: [Poll] What's the best symmetric cipher?
said by boomerbubba  :
1) Is the security/insecurity of my suggestion purely a matter of the quality of the PRNG? Or is it that there is no such thing as an acceptable PRNG for these purposes?
Well, the problem is that its still PRNG. It has to be. If it was RNG, then you couldnt agree upon it and you would have to change keys in beforehand (like true OTP). As it is PRNG, it can be cracked open. It is very, very hard to determine how secure PRNG is so its very hard to tell what kinda security it would give.
quote:
2) If a good PRNG method does exist and is publicly known, what if the methodology is changed to: Use that PRNG, and the secret symmetric key is the the seed value?
Still the same problem exists. Its PRNG. Something quite similiar to what you are saying is actually RC4 or C4 cipher used in SSL/TLS connections (https that is). It basicly a PRNG which output is XOR:ed to datastream. 
Something related to this is Jaxor. Its encryption program that I have designed (it should be out...some time...).
»www.markusjansson.net/erecent.html#jaxor
"Basicly what we are talking here is using the one-way hash function to create pseudorandom keys which are then XOR:ed to datastream. The "master key" (passphrase) is salted using the just created ciphertext to make new keys. "
Its actually very secure cipher. The security of these kinda of ciphers relies on the security of the hash function, since the hash function is the source of PRNG data. If the hash function is good, then its practicly RNG. But not in theory. Very close to RNG but not RNG...
quote:
I'm not being argumentative. Rather, I'm glad to have a forum where I can ask questions like this. (I would be driven out of sci.crypt as a hopeless newbie.)
And Im glad that we can have this kinda discussion here! Im a bit tired to all these "help, Im under attack because someone hit my port 2222 with a packet" -discussion we see too often... 
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[text was edited by author 2002-11-25 14:14:53] |
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boomerbubba
join:2001-06-15
Austin, TX
| reply to jansson_mark
said by jansson_mark :
said by boomerbubba :
A One Time Pad, generated by some proprietary PRNG method known only to the parties involved in the communication.
It might be very secure or it might be very insecure. I would not advice on using such method.
Markus, a couple of follow-up questions:
1) Is the security/insecurity of my suggestion purely a matter of the quality of the PRNG? Or is it that there is no such thing as an acceptable PRNG for these purposes?
2) If a good PRNG method does exist and is publicly known, what if the methodology is changed to: Use that PRNG, and the secret symmetric key is the the seed value?
I'm not being argumentative. Rather, I'm glad to have a forum where I can ask questions like this. (I would be driven out of sci.crypt as a hopeless newbie.)
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MeeToo7
You Too?
Premium
join:2000-10-18
Ardmore, PA
clubs: 
| reply to jansson_mark
Ok, I see I went in over my head with you
I'm obviously not as much into encryption as you are. I'm not using PGP or any encryption anymore, my knowledge is limited and haven't kept up with it.
Continue on
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jansson_mark
Markus Jansson
Premium
join:2001-08-05
Finland
| reply to MeeToo7
said by MeeToo7 :
You're poll question is misleading. Your categories are comparing apples and oranges.
No Im not.
quote:
First, AES is not an encryption algorith itself, but a name to be given to the best contenders of encryption, it stands for Advanced Encryption Standards.
Yes, I know. I thought about calling it Rijndael but since most people dont know what it is, I desided to use the AES term.
quote:
Second, Twofish is an evolution on Blowfish. It's been considered so good that it was encluded in PGP before AES was finalized.
And DES is an evolution of Lucifer. And MARS is a evolution of perhaps most of the other ciphers in the world today. They are still different ciphers. Besides, many people concider Blowfish better than Twofish, because Blowfish has longer track record.
quote:
Single DES is old news, it was cracked in a single day using an EFF machine. Don't know if 3DES has been cracked yet, but it seems pretty impossible to me, as it was said to take the time of the age of the universe to decipher, just a couple years ago.
When referring to 3DES, the DES is the algorithm. One could also ask do you prefer 3Skipjack or Skipjack...thats insane. The algorithm is still the same one.
quote:
But the power of computers seem to advance at light speed to me. I think this phenomenon is called Moore's Law? (The underestimation of computer power.)
True. However, there are much more efficient ways of breaking a modern cipher than brute forcing it.
quote:
CAST, IDEA, 3DES and Twofish haven't been cracked yet to my knowledge. The preference is subjective.
Thats why we are having this poll. I would like people to tell about why they prefer some cipher and not some other.
quote:
Some people don't like 3DES because it's based on DES, but well known experts hold it in high regards, from what I've read.
Not all experts. Finnish goverment computer security team does not recommend or permit the usage of 3DES for encrypting sensitive material. However, they do permit for example CAST5-128.
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MeeToo7
You Too?
Premium
join:2000-10-18
Ardmore, PA
clubs:
| reply to jansson_mark
You're poll question is misleading. Your categories are comparing apples and oranges.
First, AES is not an encryption algorith itself, but a name to be given to the best contenders of encryption, it stands for Advanced Encryption Standards.
Second, Twofish is an evolution on Blowfish. It's been considered so good that it was encluded in PGP before AES was finalized.
Single DES is old news, it was cracked in a single day using an EFF machine. Don't know if 3DES has been cracked yet, but it seems pretty impossible to me, as it was said to take the time of the age of the universe to decipher, just a couple years ago. But the power of computers seem to advance at light speed to me. I think this phenomenon is called Moore's Law? (The underestimation of computer power.)
CAST, IDEA, 3DES and Twofish haven't been cracked yet to my knowledge. The preference is subjective. Some people don't like 3DES because it's based on DES, but well known experts hold it in high regards, from what I've read.
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Vampirefo
Premium,MVM
join:2000-12-11
Huntington, WV | reply to jansson_mark
No problem break it down.
They are the same, just like ZA and Kerio are both firewalls, that in ways work the same, but in other ways work differently.
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jansson_mark
Markus Jansson
Premium
join:2001-08-05
Finland
| reply to Vampirefo
said by Vampirefo :
Yes they are different in some ways but they are the same type of ciphers, very small differences.
Sorry to break this to you but, no, they are not at all the same type of ciphers. They are used on totally different things and the algorithms are totally different in nature.
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Name Game
Premium
join:2002-07-07
North Myrtle Beach, SC
|  reply to jansson_mark
I will "for for" for you TomMc.. then we only have to find one more for..and that would make free..sorry... three DES>
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Steve
I'm a PC, so shut up
Consultant
join:2001-03-10
Yorba Linda, CA | reply to TomMc
said by TomMc:
How can you not have Triple DES included?
Just for for DES three times |
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TomMc
@rr.com | reply to jansson_mark
How can you not have Triple DES included? |
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Vampirefo
Premium,MVM
join:2000-12-11
Huntington, WV | reply to Steve
Yes they are different in some ways but they are the same type of ciphers, very small differences.
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Steve
I'm a PC, so shut up
Consultant
join:2001-03-10
Yorba Linda, CA
| reply to Vampirefo
said by Vampirefo :
»[Poll] What's the best asymmetric cipher?
The current poll is for symmetric ciphers: the referenced poll is for asymmetric ciphers. They're different.
Steve
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Vampirefo
Premium,MVM
join:2000-12-11
Huntington, WV | reply to jansson_mark
»[Poll] What's the best asymmetric cipher?
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Steve
I'm a PC, so shut up
Consultant
join:2001-03-10
Yorba Linda, CA
| reply to boomerbubba
said by boomerbubba :
A One Time Pad, generated by some proprietary PRNG method known only to the parties involved in the communication.
If it uses pseudo-random number generator, it's not a one-time pad. Plenty of ciphers have been broken by cracking the PRNG. Only truly random (e.g., not calculated in software) inputs are allowed, such as something that measures radioactive decay.
Steve
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LowWaterMark
Premium
join:2002-05-16
Wallingford, CT
| reply to jansson_mark
I prefer one-way encryption. No decrypt option. That way, no one can ever figure out what it says. It's a similar concept to WOM (write-only memory).
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jansson_mark
Markus Jansson
Premium
join:2001-08-05
Finland
| reply to boomerbubba
said by boomerbubba :
A One Time Pad, generated by some proprietary PRNG method known only to the parties involved in the communication.
It might be very secure or it might be very insecure. I would not advice on using such method.
But our military messaging system (SanLa) uses encryption somewhat similiar than that. It uses symmetric cipher(s) and "matrix" to encrypt. First the message is encrypted using symmetric ciphers and then that mess is encrypted using "matrix" similiar to that you descibed here. Without knowing the exact nature of the "matrix", its a pain in the *** to try to break it, since the message is already a mess before its putted throught the "matrix", so in practice you cant know when you have managed to "break" the "matrix" so you could start trying to break the symmetric cipher(s). Hehehehehee...
btw. did you know that the only cipher that "anti-Allieds" side used that wasnt broken during the WWII, was Finnish cipher? It was called "worm box" and was used until 1980:s.
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boomerbubba
join:2001-06-15
Austin, TX | reply to jansson_mark
A One Time Pad, generated by some proprietary PRNG method known only to the parties involved in the communication.
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Lithp
Thay It...Thay It
join:2001-11-22
Beverly Hills, CA | reply to jaykaykay
twofish |
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jaykaykay
4 Ever Young
Premium,MVM
join:2000-04-13
Scottsdale, AZ
 ·Speakeasy
| reply to jansson_mark
Ah! Good bedside reading. Thank you. I am not certain I will understand all that you've given me, but I shall make a good stab at it.
As far liking something NSA made, that's good thinking. Your point 2 says it all and quite well.
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jansson_mark
Markus Jansson
Premium
join:2001-08-05
Finland
| reply to jansson_mark
My favorite is Skipjack. Why?
1) It was made by the NSA
2) They know how to crack codes and they know how to make them.
3) They didnt believe it would be published in open
Only downside is relatively small keysize (80bits), but if you would implement it like Skipjack -> 3Skipjack (like DES -> 3DES) then...
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