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} }