December 2003 - cypherpunks-legacy

Re: Zimmerman on the Hill....(the details)
by djw＠eff.org 17 Dec '03

17 Dec '03

Phil Zimmermann will be testifying Tuesday October 12th at 1:30 pm: Rayburn Room 2172 House Foreign Affairs Committee Subcommittee on Economic Policy, Trade, and the Environment Also featured will be demos of DES downloaded from foreign ftp sites and a large array of foreign-produced DES-based security packages. [It's always wise to check the room assigned on the day of the hearing.] ................................................................... Daniel J. Weitzner, Senior Staff Counsel <djw(a)eff.org> Electronic Frontier Foundation 1001 G St, NW Suite 950 East Washington, DC 20001 202-347-5400 (v) 202-393-5509 (f)

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Re: RSA Security
by doug＠netcom.com 17 Dec '03

17 Dec '03

peb(a)PROCASE.COM (Paul Baclace) said: >Yes, but consider that being world famous has its advantages for contracting >and lecture fees... That's also more attractive considering that the U.S. government is quite capable of demanding the secret of the factorization method and generally throw their weight around as "justified" by national security... I'm not generally very paranoid, but I *would* be in a situation like that. Just about any and all other laws go out the window once they invoke national security. Doug -- Doug Merritt doug(a)netcom.com Professional Wild-eyed Visionary Member, Crusaders for a Better Tomorrow (The above is a joke; the following are mailing lists:) Unicode Novis Cypherpunks Gutenberg Wavelets Conlang Logli Alife HC_III Computational linguistics Fundamental physics Cogsci SF GA VR CASE TLAs

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Re: Breaking DES
by smb＠research.att.com 17 Dec '03

17 Dec '03

My understanding of how an exhaustive search on the key space can be used to break DES is that for every key, K, D(K,Cipher) is applied until the output matches something legible. Say that some random string, to be thrown out, is added to the beginning of the plain text, and that DES is applied in cbc mode, then how could such an attack work? My point, I don't see how DES can be broken if the initial block is a grabage block, and cipher block chaining is used. Please enlighten me (gently). One other point... is the decision to encrypt - decrypt -encrypt when applying triple des arbitrary? Why not just encrypt with k1 and then encrypt with k2. Isn't the effect the same? There are two reasons for that, one of which no longer applies. The one that still matters is that if you set k1==k2, then the operation is equivalent to single encryption with k1, thus providing backwards compatibility. The other reason is that it was initially feared that DES was a group. That is, encryption with k1 and k2 might be equivalent to single encryption with some unknown (to you and me) key k3. But a cryptanalyst or a brute- force cracker would neither know nor care that you double-encrypted. It has now been proved that DES is not a group. What isn't clear to me is whether it's ``mostly closed'', though I suspect not.

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Security through obscurity
by an41418＠anon.penet.fi 17 Dec '03

17 Dec '03

I know that it is pretty much accepted by the security community that security through obscurity is useless. There are countless references to this, and it is a strong argument in favor of publishing algorithms. >From time to time, however, it is healthy to question policies such as these and ask ourselves whether or not this is a good idea. It seems that Denning has changed her mind on this by advocating the secrecy of the skipjack algorithm. All of the known plaintext attacks on algorithms such as DES, that involve exhaustive key search are based on knowledge of the algorithm. Wouldn't keeping the algorithm a secret render such chips, as the one presented in Eurocrypt '93 useless? I agree that analysis is more difficult when you don't know if an intruder has compromised your algorithm, but if it were my data that I wanted kept secret I wouldn't give the cracker a head start by publishing my algorithm. Clipper has proven how difficult it is to reverse engineer an algorithm. Let me just say that I know I have violated an accepted doctrine of computer security, but I think it's okay to question even the most accepted ideas every once in a while. I thought this would be a bit provocative. Wonderer ------------------------------------------------------------------------- To find out more about the anon service, send mail to help(a)anon.penet.fi. Due to the double-blind, any mail replies to this message will be anonymized, and an anonymous id will be allocated automatically. You have been warned. Please report any problems, inappropriate use etc. to admin(a)anon.penet.fi.

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Re: PGP misunderstanding
by M. Strata Rose 17 Dec '03

17 Dec '03

Derek writes: And just what is the point of an encrypted newsgroup? What key(s) would you use to encrypt the messages, and why? I would create a pair of keysets, VCNPoster and VCNReader and have both the public and private keys accessible via finger. The outbound news would be encrypted as if these two nyms were exchanging messages. It's not a security thing, it's just that people who won't bother to learn how to use the technology won't be able to read or post there. That will be enough incentive to get another class of folks using it, IMHO. _Strata M. Strata Rose Unix & Network Consultant, SysAdmin & Internet Information Virtual City (TM) Network strata(a)virtual.net | strata(a)hybrid.com | strata(a)fenchurch.mit.edu

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Re: Breaking DES
by an41418＠anon.penet.fi 17 Dec '03

17 Dec '03

I am sorry to have asked two questions in my original post. A few people have made me aware of the reason for encrypting EDE in triple DES for backward compatability and the issue of whether or not DES is a group. So, I'd like to redirect this thread to my other question: My understanding of how an exhaustive search on the key space can be used to break DES is that for every key, K, D(K,Cipher) is applied until the output matches something legible. Say that some random string, to be thrown out, is added to the beginning of the plain text, and that DES is applied in cbc mode, then how could such an attack work? My point, I don't see how DES can be broken if the initial block is a grabage block, and cipher block chaining is used. Please enlighten me (gently). Wonderer ------------------------------------------------------------------------- To find out more about the anon service, send mail to help(a)anon.penet.fi. Due to the double-blind, any mail replies to this message will be anonymized, and an anonymous id will be allocated automatically. You have been warned. Please report any problems, inappropriate use etc. to admin(a)anon.penet.fi.

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Why X/Open in London?
by Duncan Frissell 17 Dec '03

17 Dec '03

I noted that Novell was supposed, today, to assign its rights to Unix to the X/Open consortium based in London. You don't suppose that X/Open was founded in London so that future Unix versions could integrate crypto without bothering with US export laws. <G> Another blow to America's competitiveness. Duncan Frissell --- WinQwk 2.0b#0

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Re: The Bank of the Internet!?
by lefty＠apple.com 17 Dec '03

17 Dec '03

Harry S. Hawk writes: > >I don't, however, see how any of this could impact a simple credit >union type bank opperated over the Internet. I would be surprised to discover that running a bank "over the Internet" didn't stand a fair chance of running afoul of interstate banking laws... -- Lefty (lefty(a)apple.com) C:.M:.C:., D:.O:.D:.

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Re: Security through obscurity
by an38793＠anon.penet.fi 17 Dec '03

17 Dec '03

> You are not going to be able to keep your algorithm secret, period. > Those who are determined enough will be able to dig it out of any > programs or chips you use to implement your algorithm. Security through > obscurity is stupid because no matter how smart you may think you are > in hiding your method, there is always someone smarter who will dig it > out and changing technology constantly lowers the barrier of how smart > people need to be to dig information out of old locks using new tools. I agree with this 100%. The interesting fact is, a lot of commercial programs rely on security through obscurity. Often, anyone who takes the time to disassemble the interesting routines, can crack the encryption. Yes it is stupid. But, a lot of people and companies rely on "security through obscurity" to protect their applications/data. Part of this is due to export restrictions, but a large part is just due to lack of awareness. One of my favorite applications has embedded in its license agreement: "...nor shall the Licensee attempt to decrypt any Passwords that may enable the Software's functionality..." This is not a substitute for real security. ------------------------------------------------------------------------- To find out more about the anon service, send mail to help(a)anon.penet.fi. Due to the double-blind, any mail replies to this message will be anonymized, and an anonymous id will be allocated automatically. You have been warned. Please report any problems, inappropriate use etc. to admin(a)anon.penet.fi.

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Re: Breaking DES
by smb＠research.att.com 17 Dec '03

17 Dec '03

My understanding of how an exhaustive search on the key space can be used to break DES is that for every key, K, D(K,Cipher) is applied until the output matches something legible. Say that some random string, to be thrown out, is added to the beginning of the plain text, and that DES is applied in cbc mode, then how could such an attack work? My point, I don't see how DES can be broken if the initial block is a grabage block, and cipher block chaining is used. Please enlighten me (gently). The decryption equation for CBC mode is P[n] <- D(C[n]) ^ C[n-1] In other words, decrypt the current ciphertext block, and XOR with the previous ciphertext block. Note carefully: the previous ciphertext block. That implies that you can start at any point in the string and do your decryption. You don't have to know the plaintext of the previous block to proceed, which is what you're implying. The property of CBC mode is related to its error propagation character- istics, which are important in some environment. Suppose that ciphertext block C[n] is garbled, either by a bird sitting on a phone line or by hostile action. That will garble two blocks of output: P[n] and P[n+1]. (Derivation is left as an exercise for the reader.) But P[n+2] will be decrypted properly, since it depends on P[n+1] and P[n+2]. (N.B. I'm deliberately ignoring insertion/deletion errors. If those are a concern, use CFB mode.) In accordance with my usual habits, I'll cite an excellent reference on how to use cipher systems, and what the properties of the different encryption modes are: @book{daviesprice, author = {Donald W. Davies and Wyn L. Price}, edition = {second}, publisher = {John Wiley \& Sons}, title = {Security for Computer Networks}, year = {1989} } Bruce Schneier's excellent book ``APPLIED CRYPTOGRAPHY: PROTOCOLS, ALGORITHMS, AND SOURCE CODE IN C'' is due out next month; it covers this, too. (I'll forbear to cite my own book till it's nearer completion...)

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