Thread View: sci.crypt
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Started by The Jester
Tue, 29 Sep 1992 08:21
What public key is REALLY good for
Author: The Jester
Date: Tue, 29 Sep 1992 08:21
Date: Tue, 29 Sep 1992 08:21
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4349 bytes
The question I pose in this post is:What is the proper role of Public Key Encryption in an environment where absolute key verification on a wide scale is not feasable. Before I address this question I would like to point out a particular case that I will NOT deal with. This case involves two entities who wish to securely communicate and have extensive previous contact. This situation affords several secure means of key transmission. This situation is actually particularly well suited to the use of public key encryption if an intial 'secure' key transmission can be reasonable guaranted. However this issue has been delt with in many other papers, posts, and so on, and need not again be addressed here. With that particular case out of the way, I shall first define why I believe that the internet environment is not suitable for any form of key verification on a 'grand' scale: The most important aspect of key verification is the trust factor, person A trusts Person B who trusts & verifys person C's key. Thus person A is supposed to accept C's key with B's validation. This chain can be extended infinitely. Unfortunatly if the chain should break at any point, the entire security of the system will collapse. Though it is theoretically possible to produce redundancies in the system to lessen the likelyhood of such a collapse. In practice it is impossible to implement. The average use may know many people on the net, but they do not know them personally and in almost all cases most certainly don't know them well enough to 'trust' them. In addition the very concept of 'trust' is faulty as it relies upon the judgement of many individuals, any one of whom may be either untrustworthy themselves or may have accepted as trustworthy an untrustworthy individual. In addition the concept of 'levels' of trust introduced in PGP does not aid the situation any as the 'level of trust' of a system will always be that of the lowest part of that system. Thus it is fair to assume that in the general circumstance it is impossible for any real verification of key authenticity to occur. This having been said, the inevitable question is:What then is the purpose of public key encryption in such an environment? The answer is one of deterance. The main reason given for the use of public key is to prevent nosy sysops and the NSA (and other related federal, state, and local agencies) from having ready access to communications. Even assuming a situation such as the one that currently exists on the net where key authorization is not used. This still prevents a strong deterant against invasion of privacy by various agencies, IF encryption is used on a large scale. Assuming that many keys have been violated, the NSA or related organization would be required to keep records on what keys belonged to who, it would have to update it's own records as keys are changed, it would have to actively decrypt ALL mail, and so on and so forth. As long as the process of changing keys once they have been distributed does not become too mechanized (i.e. your software will not automatically mail all your friends telling them that after two years your changing to a different key, and then have your friend's software automatically update their files (if you can do it, so can the NSA)) the organizational and computational challenges would quickly prove to be a nightmare. In addition those individuals with a more definite reason to fear surveilance can take stronger measures to protect their privacy. However the general case is what is most important here. Wide spread use of public key encryption, even if key security is relatively weak, will prove to make wide spread surveilance infeasable. Yaron (The Jester) Goland -- The Jester "Freedom isn't Free"-The U.S. Army "Nothing is too wonderful to be true"-Faraday "If I knew it all, what would I be doing HERE?"-The Jester
Re: What public key is REALLY good for
Author: Stephan Neuhaus (HiWi Mattern)
Date: Wed, 30 Sep 1992 12:17
Date: Wed, 30 Sep 1992 12:17
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ygoland@edison.seas.ucla.edu (The Jester) writes: >[Lots of stuff with which I basically agree] However, you also write, >The most important aspect of key verification is the trust factor, >person A trusts Person B who trusts & verifys person C's key. Thus person A >is supposed to accept C's key with B's validation. This chain can be >extended infinitely. It *can*, but only if you (A) allow introducers (B) to introduce introducers (C). PGP has a parameter in its config.txt file that allows you to tell PGP how deep the certification process may become (it's called CERT_DEPTH I think, and its default is set to 4). Furthermore, there is a difference between the *validity* of a key and the *trust* you put in its owner. You may believe that a certain key is from Billy, but wouldn't trust Billy to sign any other keys competently. On the other hand (this is far-fetched), you might trust somebody's ability at key management but might believe that his key has been exposed or otherwise cracked. Have fun. -- Stephan <neuhaus@informatik.uni-kl.de> sig closed for inventory. Please leave your pickaxe outside. PGP 2.0 public key available on request.
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