Multiple recipient message encryption

A method comprising:

• with a server of a security authority, receiving a different encryption key for each of a plurality of parts of an encrypted e-mail message from a computing system of an e-mail service provider, the encrypted e-mail message having a plurality of recipients, wherein each recipient of the plurality of recipients is a group within an organization where each group contains an email list, wherein the plurality of recipients do not receive different encrypted e-mail messages;
• with the server, receiving a generated alpha-numeric part identifier for each of the plurality of parts of the encrypted e-mail message;
• with the server, receiving access privileges for a first recipient of the plurality of recipients, the access privileges for the first recipient identifying which parts of the encrypted e-mail message the first recipient is authorized to access;
• with the server, receiving, from a client device of the first recipient, a request for an encryption key for a first part of the plurality of parts from the encrypted e-mail message and an encryption key for a second part of the plurality of parts from the encrypted email message;
• in response to determining, based on the access privileges and the part identifier for the first part, that the first recipient is authorized to view the first part, transmitting to the recipient the encryption key for the first part;
• in response to determining, based on the access privileges and the part identifier for the second part, that the first recipient is not authorized to view the second part, withholding the encryption key for the second part;
• with the server, receiving, from a client device of an additional user to whom the e-mail message has been forwarded, a request for the encryption key for the first part of the plurality of parts from the encrypted e-mail message and the encryption key for the second part of the plurality of parts from the encrypted email message, the additional user being different from any recipient on the list of recipients;
• and
• in response to determining that the additional user is not authorized to view the first part, based on the access privileges and the part identifier for the first part, withholding the encryption key for the first part.

A method performed by a computing system, the method comprising:

• receiving from a client device of a user, a plurality of content parts of an e-mail message;
• generating and assigning to each of the plurality of content parts, a part identifier that uniquely identifies one of the content parts with an alpha-numeric value;
• associating with each of the plurality of content parts, a different encryption key;
• receiving, from the client device of the user, a list of recipients of the e-mail message and access privilege data associated with each recipient of a plurality of recipients in the list, the access privilege data indicating which of the plurality of content parts each recipient is authorized to access, wherein each recipient is a group within an organization where each group contains an email list;
• transmitting the e-mail message to a server without sending multiple different e-mail messages to the server;
• transmitting the access privilege data, the different encryption key for each of the plurality of content parts, and the part identifier for each of the plurality of content parts to a server of a security authority;
• with the server, receiving a request from a client device of a recipient of the list of recipients to decrypt the e-mail message, the request including the part identifier for each of the plurality of content parts;
• with the server, based on the part identifier and the access privilege data, transmitting to the client device of the recipient an encryption key for a part the recipient is authorized to view and withholding an encryption key for a part the recipient is not authorized to view;
• with the server, receiving another request from a client device of an additional user to whom the e-mail message has been forwarded, the another request including the part identifier for each of the plurality of content parts, the additional user being different from any recipient on the list of recipients;
• and
• with the server, based on the part identifier and the access privilege data, withholding an encryption key for a part the additional user is not authorized to view.