This is unclear.  A trusted authority, at least within my limited scope, has been defined as a large organization (as opposed to an individual), or a provably secure software agent. So the man-in-the-middle attack is certainly possible, but a whole host of people have to be in on the scam. I suppose so few people responded to this one since it's so blatantly wrong ... but it bothers the heck out of me.  Large != trustworthy, and I'll decide who I trust if you please.  And provably secure software is one of those urban legends.

and (b) that Bank A is a trustworthy inividual to sign the certificate in the first place. My understanding is that the TTP will be the body that allows this, banks will most certainly be CAs but there will still need to be a body above them. I don't think a trusted third party is required in this situation, though it's true that A and B have to be able to trust each other, or at least the validity of the certificates passed between them. Bank A and Bank B need to formally (either with a signing of contracts or a shaking of hands, etc) recognize each other as 'trusted'.  They do this _before_ customer A wants to do business with customer B, in lieu of going through the 'trusted third party' bottleneck. In X509v1, there was no way to extend certificates beyond the core specification, but this has changed.  In X509v3 there is a way to attach extra information at the end of a certificate, and this is relevant. CAa is the CA owned and operated by bank A, and CAb is the CA owned and operated by bank B.  A customer of Bank A needs to verify the legitimacy of a certificate given to him by a customer of Bank B.  The extra attributes in X509v3 certs can be used to establish chains of trust . The aggreement between Bank A and Bank B can be reflected in a certificate attribute.  Customer A checks the attribute list at the end of customer B's certificate, looking from an endorsement from CAa (the bank already trusted by customer A).  That endorsement would be verifiable, as it would be signed by CAa.  If customer A did not find such an endorsement, he would call Bank A and complain, much in the way people call up their local cable operator and ask for subsciptions to M2...  Bank A, in the interest of keeping the business of customer A, would investigate Bank B and attempt to forge an agreement. corollary:  bank A does not have to _directly_ trust bank B.  if bank A trusts a bank that trusts bank B, customer A has reason to trust bank B. it is at the discretion of customer A to accept or reject such an endorsement, just as it is at customer A's discretion to accept or reject the endorsement of Bank A itself.  the chains of trust are of variable length. -Jared The problem I see with this is that the certificate may potentially be quite large an complex if more than one organisation is brought into the picture. With a TTP _style_ set up, the certificate could contain the CA who issued it and the body (PCA) who 'vouches' for them.  In this manner the certifica can be kept quite compact whilst the chain of trust is maintained. The problem comes down to who do you ultimately trust.  Your certificate could potentially be used as a form of Digital ID as it verifies your physical identity to the on-line world (assuming there is a smartcard _link_ or some mechanism that makes it difficult for other individuals to appropriate your 'identity').  In order for this system to work effectively, the person receiving your certificate needs to have some level of confidence that whomever issued it can also be trusted and so it goes. The TTP system (&X.509 heirachy) provides a mechanism for doing this.  I see the greatest difficulty in with certificates as being procedural rather than technological i.e. what measures are the governments etc going to put in place so that I can be sure that the person I am interacting with is genuine.  This is a policy and policy enforcement issue.

As the case a few years ago in England establishes, if you allege that some of your money has disappeared, and you cannot *prove* that you didn't withdraw the money yourself, some banks would rather sue you for fraud {for attempting to gain money from them without having proved that you are owed it} instead of co-operating with you to establish the loss. Hi! Could you pls provide a searchable reference for this? Thank you, Ed ______________________________________________________________________ Dr.rer.nat. E. Gerck                     This e-mail address is being protected from spam bots, you need JavaScript enabled to view it http://novaware.cps.softex.br    

1. Money: This apparent contradiction dissolves when we remember that bank notes were a legal tender for gold until rather recently and so people developed trust in money because governments would guarantee their payment in gold. Just a little note. I remember (vaguely) that sometime previously the US bank notes contained a statement garanteeing their value in terms of gold and that that promise was revoked later. (I guess many of you know the history better than I do.) I am not sure whether that didn't have grave consequences to some people. So faith has to be something not very well-defined, I suppose. In almost all countries money gets devaluated with time. The inflation is mild in some and drastic in others. Somehow one loses the sensitivity to that phenomenon though. (Analogous e.g. to the fact that with time I don't have problems to fall asleep although my apartment is in an extremely noisy part of the city.) M. K. Shen ______________________________________________________

: As the case a few years ago in England establishes, if you allege that : some of your money has disappeared, and you cannot *prove* that you : didn't withdraw the money yourself, some banks would rather sue you for : fraud {for attempting to gain money from them without having proved : that you are owed it} instead of co-operating with you to establish the : loss. :Could you pls provide a searchable reference for this? http://catless.ncl.ac.uk/Risks is the official comp.risks archive, but unfortunately its search engine is line-at-a-time.

1. Money: This apparent contradiction dissolves when we remember that bank notes were a legal tender for gold until rather recently and so people developed trust in money because governments would guarantee their payment in gold. Just a little note. I remember (vaguely) that sometime previously the US bank notes contained a statement garanteeing their value in terms of gold and that that promise was revoked later. (I guess many of you know the history better than I do.) I am not sure whether that didn't have grave consequences to some people. So faith has to be something not very well-defined, I suppose. In almost all countries money gets devaluated with time. The inflation is mild in some and drastic in others. Somehow one loses the sensitivity to that phenomenon though. (Analogous e.g. to the fact that with time I don't have problems to fall asleep although my apartment is in an extremely noisy part of the city.) M. K. Shen To continue on this tangent, the gold standard was revoked because France (under DeGual (sic) I believe) had started stockpiling gold notes from other countries by buying them above market value. The goal was to get a massive amount of gold backed notes, cash them in for an equal amount of gold and in the process screw every other country's currency, leaving france with all the gold. It just so happened that the US president at the time decided to switch the currency off the gold standard just before France could pull off its little trick (imagine that.. Anyway it was bound to happen any ways because of the fact that there is only a limited amount of gold in the world (e.g. if today's money was backed by gold there wouldn't be enough gold available to back all the money if people decided to all cash in their notes). End Tangent now back to our regularly scheduled sin