[81953] in Cypherpunks
Re: keeping secrets and knowing when they're compromised
daemon@ATHENA.MIT.EDU (Peter Trei)
Tue Jun 17 11:03:54 1997
From: "Peter Trei" <trei@process.com>
To: dcoe@overlord.com, cypherpunks@sirius.infonex.com
Date: Tue, 17 Jun 1997 09:48:03 -6
Cc: trei@process.com
Reply-To: "Peter Trei" <trei@process.com>
nobody@huge.cajones.com (Huge Cajones Remailer) wrote:
> I want to encrypt and give to a "friend" some computer documents that
> are only to be decrypted and used by that person if something terrible
> happens to me.
>
> I also want to know, if I'm still around, when and if those documents
> are decrypted. I.e. In the event that my friend isn't as trustworthy
> as I presume, I want to find out if s/he decrypts the files while I'm
> still around.
>
> I know I could put the key in escrow somewhere, but would prefer not
> to involve a third party. Any ideas?
The following presumes that there are at least two people who you trust
to follow instructions, and to keep quiet about their involvment in the
scheme, but not to hold the complete data.
Encrypt your data using key#1. Encrypt key#1 with key#2.
Give the encrypted data, and key#2 to Trusted Agent (TA) #1.
Give the encrypted key#1 to Trusted Agent #2. If 'something terrible'
happens to you, TA#2 posts the ecrypted key to alt.anonymous.messages,
with a specific title.
After 'something terrible' happens to you, TA #1 watches a.a.m for
the specified title, decrypts key#1 using key#2, uses key#1 to decrypt
the data, and takes the appropriate actions.
Neither of the TAs can decrypt the data alone, and they can be
unknown to each other, which makes if difficult for them to
collude. You could get fancy, and use secret sharing to spread the
data or key among more people.
I think you could call this the 'Thomas Crown' technique (obscure 60's
reference).
Peter Trei
trei@process.com
