On 10/09/13 10:00, Guido Witmond wrote:
Hi Peter,

We really have different designs. I'll comment inline.

On 09/09/13 19:12, Peter Fairbrother wrote:
On 09/09/13 13:08, Guido Witmond wrote:

I like to look at it the other way round, retrieving the correct
name for a key.

You don't give someone your name,

sorry, that should read "You don't give someone your address or telephone number". mea culpa. You can give them your name.

you give them an 80-bit key
fingerprint. It looks something like m-NN4H-JS7Y-OTRH-GIRN. The m-
is common to all, it just says this is one of that sort of hash.

There is only one to remember, your own.

If I read it correctly, each participant has one *single identity*?

Yes - except of course you can have as many identities as you want. You create them yourself after all.

The only assurance given by the scheme is that if a person gave you a hash which he generated himself, and you match it with a string and that string matches what you know about the person (eg their name or photo), then no-one else can have MTM'd it.

(maybe the server returns two or three matches, as after a while there will be random birthday collisions. That's why you should check the string matches what you know about the person. But an attacker can't find a hash which matches a particular pre-chosen person by trying, it would take 2^100 work)

You can have one for business, one for pretty girls, one for ugly girls - you just have to remember them all (except maybe the one for ugly girls). Or you can write them down. Or put them on your business card.

The point is that for practical purposes the hash *is* your telephone number, and/or your email, and/or your facebook page - we just need to get everyone else to install the software to do the lookup, checking, translation etc automagically and behind the scenes in their telephones, browsers, email clients etc.

(this was originally designed only for use in a single semi-secure comms program suite - but I don't see why it couldn't be more widely used)

As you and I have never met, I can't validate your photo, neither half
your claimed penis size. ;-)

How do I know it's not a Man in the Middle using your picture?

See above. It would take on average 2^79 operations each of which would require 2^20 work to find a matching hash, starting with a picture. Or even just starting with a name, or whatever.

-- Peter Fairbrother
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