31. A content server for use in a secure distribution system that distributes digital content over a network to a user running a browser program in a workstation connected to the network, the content server comprising: a publishing tool that accepts plaintext documents, encrypts the plaintext documents and generates document identifiers for each encrypted document wherein each document identifier is calculated for each encrypted document as a result of a numerical computation using as one input the encrypted document content and as another input information that is not part of the encrypted document content, so that the document identifier cannot be derived solely from the encrypted document content; means for downloading a secure viewer program and the information that is not part of the encrypted document content into the browser; means responsive to a document request from the viewer program for downloading an encrypted version of the requested document containing encrypted content; means for receiving a document identifier that is computed in the viewer program as a result of a numerical computation using as one input the encrypted content and as another input the information that was downloaded with the viewer program, but which cannot be derived solely from the encrypted version of the requested document from the viewer program; and means responsive to the document identifier for downloading a decryption key to the viewer program.
31. A content server for use in a secure distribution system that distributes digital content over a network to a user running a browser program in a workstation connected to the network, the content server comprising: a publishing tool that accepts plaintext documents, encrypts the plaintext documents and generates document identifiers for each encrypted document wherein each document identifier is calculated for each encrypted document as a result of a numerical computation using as one input the encrypted document content and as another input information that is not part of the encrypted document content, so that the document identifier cannot be derived solely from the encrypted document content; means for downloading a secure viewer program and the information that is not part of the encrypted document content into the browser; means responsive to a document request from the viewer program for downloading an encrypted version of the requested document containing encrypted content; means for receiving a document identifier that is computed in the viewer program as a result of a numerical computation using as one input the encrypted content and as another input the information that was downloaded with the viewer program, but which cannot be derived solely from the encrypted version of the requested document from the viewer program; and means responsive to the document identifier for downloading a decryption key to the viewer program. 32. The content server of claim 31 further comprising a key database and wherein the means for downloading a decryption key comprises means for using the document identifier to retrieve the decryption key from the key database.