OSEC

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Crypto Archives: Re: Electronic envelopes

Re: Electronic envelopes

Sean Kelly (sean.kmindspring.com)
Sat, 25 Sep 1999 20:45:47 -0400

At 05:51 PM 9/25/99 +0200, Mok-Kong Shen wrote:
>I like to know whether it is possible (and how) to realize an
>electronic envelope in the following sense: It is not possible by
>anyone else than the sender to get the contents of the envelope
>before a predetermined time point without that act of manipulation
>be known.
...
>After deposition of the envelope, no further interaction
>between the sender and the notary is assumed to be available.

I can envision physical constructs that might be possible: a fancy safe
with a time-lock whose contents would be destroyed if tampered with. But
in software...

In either situation there are two possibilities: a device that keeps track
of time internally (ie. a safe or in the case of code a running program) or
a passive device that relies on external cues for the current/elapsed
time. In software, both situations could be worked around. If it's a
running piece of code, someone with enough skill could modify bits of
memory of the running program to fool the clock. If it uses an external
cue (simplest case being the system time) then that cue could be
faked. ie. it doesn't matter how well-encrypted the contents are, the key
is either a number of elapsed ticks or the current time.

It is an interesting problem... can anyone suggest something that I'm
missing? I'd love to hear it.

Sean

This archive was generated by hypermail 2.0b3 on Sat Sep 25 1999 - 22:36:55 CDT