Gautam R. Singh <gautam.singh () gmail com> wrote:
I was just wondering is there any encrytpion alogortim which expires
For example an email message maybe decrypted withing 48 hours of its
delivery otherwise it become usless or cant be decrypted with the
Lets imagine there is a "trusted", non-hackable third-party which
timestamp database along with private/public keys. Lets cal it Trent.
manages timestamps in terms of existence and validity. Each timestamp
only be used once and only once. Each timestamp, as soon as it is
has also associated a validity window outside of which it will be
as invalid. Whenever a timestamp its checked for existence, it will be
marked as used, and hence becomes invalid afterwads. Each timestamp is
Alice has a message. Alice asks Trent for a timestamp. She generates a
of the message, and then she signs the hash and the timestamp with her
private key. She sends the message and the signature to Bob.
When Bob receives the message, Bob decrypts the signature with Alice's
public key and sends Trent the timestamp for validity check. Trent
associated timestamp in its database, sends Bob a positive response and
invalidates the timestamp.
While Bob wants to be sure the message originates from Alice, Alice
the message to be valid (as originating from her) for only a certain
If a certain validity (48h) is given to the timestamps, this may lead
valid solution for the situation described above.
How reasonable is this?