	US 7,613,304 B2
	System and method for sending encrypted messages to a distribution list
Neil P. Adams, Waterloo (Canada); Michael S. Brown, Waterloo (Canada); and Michael K. Brown, Kitchener (Canada)
Assigned to Research In Motion Limited, Waterloo, Ontario (Canada)
Filed on Mar. 08, 2005, as Appl. No. 11/73,677.
Prior Publication US 2006/0204011 A1, Sep. 14, 2006
Int. Cl. H04L 9/08 (2006.01)

U.S. Cl. 380—282

19 Claims

1. A method of sending encrypted messages from a mobile communication device utilizing a distribution list, the method comprising:

identifying a distribution list address in a message;

determining one or more member addresses associated with the distribution list address;

for each member address, determining if a public key for a member identified by the member address is available on the mobile communication device;

for each member whose public key is available on the mobile communication device, encrypting the message to the member by employing asymmetric encryption at the mobile communication device using the public key for the member;

sending the encrypted message to the distribution list address without replacing the distribution list address with member addresses if each of the one or more member addresses associated with the distribution list identifies at least one member whose public key is available on the mobile communication device;

at the mobile communication device, determining that not all members identified by the one or more member addresses associated with the distribution list are able to decrypt the message, if at least one of the one or more member addresses associated with the distribution list does not identify at least one member whose public key is available on the mobile communication device;

at the mobile communication device, expanding the distribution list address within a header of the message only after determining that not all members identified by the one or more member addresses associated with the distribution list are able to decrypt the message, by replacing the distribution list address with one or more member addresses that identify one or more members whose public key is available on the mobile communication device; and

sending the message to each of the one or more member addresses that identify one or more members whose public key is available on the mobile communication device if at least one of the one or more member addresses associated with the distribution list does not identify at least one member whose public key is available on the mobile communication device.