System and method for processing attachments to messages sent to a mobile device
A system and method for processing attachments to messages sent to a mobile device is described herein. Embodiments described herein apply to encrypted messages comprising multiple message parts, in which different encryption keys (e.g. session keys) have been used to encrypt the different message parts. In at least one example embodiment, the encrypted session keys for every message content part comprising an attachment is received at the mobile device. In one embodiment, all of the encrypted session keys are stored together in a main message header. The mobile device may then decrypt the encrypted session key associated with a user requested attachment, and transmits the decrypted session key to one or more remote servers in an attachment request for use in decrypting the requested attachment. Data associated with the requested attachment, in decrypted form, is returned to the mobile device.
1. A mobile device configured to process a message comprising a plurality of encrypted attachments received from a sender via one or more remote servers, wherein the mobile device comprises a processor and memory, and wherein the processor is configured to perform acts comprising:
receiving, from the one or more remote servers, data associated with the message, wherein the one or more remote servers are configured to initially withhold transmission of each encrypted attachment of the plurality of encrypted attachments to the mobile device until a request for the attachment is made by the mobile device, and wherein the data received from the one or more remote servers identifies an attachment structure for the message and comprises at least one encrypted session key of a plurality of session keys; and
outputting the attachment structure;
wherein the message as sent from the sender comprises the plurality of encrypted attachments, wherein each of the plurality of encrypted attachments is encrypted using a different one of the plurality of session keys, and wherein each session key of the plurality of session keys is encrypted such that the session key is decryptable with a key accessible to the mobile device but not to the one or more remote servers.
2. The device of claim 1 , wherein the data associated with the message received at the mobile device comprises an encrypted session key for each of the plurality of encrypted attachments.
3. The device of claim 2 , wherein the processor is further configured to:
receive an attachment request via a user interface of the mobile device, the attachment request identifying a specific encrypted attachment of the plurality of encrypted attachments;
decrypt the encrypted session key for the specific encrypted attachment to produce a decrypted session key;
transmit the decrypted session key with the attachment request to the one or more remote servers, wherein the one or more remote servers are configured to decrypt the specific encrypted attachment using the decrypted session key and to transmit data associated with the specific encrypted attachment in decrypted form to the mobile device; and
receive data associated with the specific encrypted attachment in decrypted form from the one or more remote servers.
4. The device of claim 3 , wherein the device is not equipped with a native attachment viewer.
5. The device of claim 3 , wherein the data associated with the specific encrypted attachment received in decrypted form from the one or more remote servers comprises text and images, which are processed by a messaging application residing and executing on the mobile device for rendering in the user interface.
6. The device of claim 2 , wherein the at least one encrypted session key received from the one or more remote servers is provided in a message header.
7. The device of claim 6 , wherein the one or more remote servers are configured to retrieve the encrypted session key for each of the plurality of encrypted attachments, and to store the encrypted session key for each of the plurality of encrypted attachments in the message header.
8. The device of claim 6 , wherein the encrypted session key for each of the plurality of encrypted attachments has been stored in the message header at a computing device of the sender.
9. The device of claim 2 , wherein the encrypted session key for each of the plurality of encrypted attachments is provided with its corresponding encrypted attachment in an associated message part, within the data received from the one or more remote servers.
10. The device of claim 1 , wherein the one or more remote servers comprises a message management server.
11. The device of claim 1 , where the one or more remote servers comprises an attachment server.
12. The device of claim 1 , wherein the message comprises a message formatted in accordance with a PGP Partitioned encoding format.
13. The device of claim 1 , wherein the message comprises an e-mail message.
14. The device of claim 1 , wherein the message comprises an instant message.
15. The device of claim 1 , wherein the message comprises a peer-to-peer message.
16. The device of claim 1 , wherein each of the plurality of encrypted attachments is formatted in accordance with a PGP Partitioned encoding format.
17. The device of claim 1 , wherein the device is not equipped with an attachment viewer.
18. The device of claim 1 , wherein the key accessible to the mobile device is stored on a smart card.
19. The device of claim 1 , wherein the key accessible to the mobile device comprises a public key of a public key and private key pair.
20. The device of claim 1 , wherein the key accessible to the mobile device comprises a symmetric encryption key.