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Re: Multikey crypto
Since I am relatively new to the field of encryption forgive
me if this is a FAQ.
Has anyone ever done anything with an encryption scheme that
allows multiple unlocking keys? What I'm thinking about is a
way to encrypt some data and then create multiple keys that
will decrypt the data. I want to be able to encrypt a document
and then give multiple people access to the document and be
able to lock out a key and/or generate new keys without having
to redistribute keys to everybody that already
has one. I realize that this makes it easier to attack the
encrypted information since there are multiple keys to unlock
the data but I don't consider this a big problem. If someone
wants to throw heavy duty horsepower at the problem they will
crack it eventually anyway.
There are a number of ways to do that. The best overview can be
found in
@incollection{Simmons92,
author = {Gustavus J. Simmons},
title = {An Introduction to Shared Secret and/or Shared Control Schemes and Their Application},
booktitle = {Contemporary Cryptology: The Science of Information Integrity},
year = 1992,
pages = {441--497},
editor = {Gustavus J. Simmons},
publisher = {{IEEE} Press}
}
The best-known scheme is described in
@article{sharesecret,
author = {Adi Shamir},
journal = {Communications of the ACM},
number = {11},
pages = {612--613},
title = {How to Share a Secret},
volume = {22},
year = {1979}
}
but also see
@article{sealing,
author = {David K. Gifford},
journal = {Communications of the ACM},
number = {4},
pages = {274--286},
title = {Cryptographic Sealing for Information Secrecy and Authentication},
volume = {25},
year = {1982}
}