If the trustee (correct word?) stops passing the messages to your "CDMS" (cryptographic dead man switch), it would simply decrypt the original message automatically. So you can not put the entire mechanism in the hands of the trustee, especially not the part that authorizes the decryption. I could imagine that you would set up a remote server that would simply send the secret to the trustee, encrypted to his public key for security, when you stop "pinging" it by sending signed messages.
To prevent one server from being compromised and revealing the secret (even if only to the trustee since it can be pre-encrypted), I could imagine chained-session Secure Multiparty Computation across several remote servers. The idea is that you run the SMPC software on your remote servers, give a large random number to each, they generate a keypair inside the virtual SMPC machine, and you encrypt the message to that key.The machines split the keypair among themselves using a Secure Sharing Scheme. You send that encrypted message to all the machines. Each day the machines re-run the SMPC, sends their key parts and reassemble them using the secret sharing scheme inside the SMPC, checks if a signed message have been recieved from you, and if not it decrypts the secret message to the trustee. A program on the machines will then see this message as the output from the SMPC and send it to the trustee. Overly complicated, maybe, but secure and can actually work. On Wed, Sep 5, 2012 at 3:51 PM, StealthMonger <stealthmon...@nym.mixmin.net>wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > > Can there be a cryptographic "dead man switch"? A secret is to be > revealed only if/when signed messages stop appearing. It is to be > cryptographically strong and not rely on a trusted other party. > > The motivating application is a Living Trust wherein the Grantor wants > to keep secret, even from the Trustee, the locations of his caches of > gold until such time as he is no longer able to send signed messages. > Each signed message has to somehow avert revelation of the secret for > another time period (three months, say). > > - -- > > > -- StealthMonger <stealthmon...@nym.mixmin.net> > Long, random latency is part of the price of Internet anonymity. > > anonget: Is this anonymous browsing, or what? > > http://groups.google.ws/group/alt.privacy.anon-server/msg/073f34abb668df33?dmode=source&output=gplain > > stealthmail: Hide whether you're doing email, or when, or with whom. > mailto:stealthsu...@nym.mixmin.net?subject=send%20index.html > > > Key: mailto:stealthsu...@nym.mixmin.net?subject=send%20stealthmonger-key > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.10 (GNU/Linux) > Comment: Processed by Mailcrypt 3.5.9 <http://mailcrypt.sourceforge.net/> > > iEYEARECAAYFAlBF1ecACgkQDkU5rhlDCl5omQCgpcuTWhFuojJkkgUOLeZwnYIf > TlwAnAhrxdyeLMccamIAZ8CbLZKn2jyb > =MaVJ > -----END PGP SIGNATURE----- > > _______________________________________________ > cryptography mailing list > cryptography@randombit.net > http://lists.randombit.net/mailman/listinfo/cryptography >
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