Method and apparatus for sending encrypted electronic mail through a distribution list exploder

• US 6,912,656 B1
• Filed: 11/30/1999
• Issued: 06/28/2005
• Est. Priority Date: 11/30/1999
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Perlman, Radia J., Hanna, Stephen R.
• Primary Examiner(s): Lamarre, Guy J.
• Assistant Examiner(s): La Forgia, Christian
• Application Number:
  US09/451,504
• Time in Patent Office: 2,037 Days
• Field of Search: 713/170, 380/20
• US Class Current: 713/170
• CPC Class Codes: H04L 2463/102 applying security measure for e-commerce data processing systems or methods, specially adapted for e-commerce G06Q30/00
• CPC Class Codes: H04L 45/16 Multipoint routing
• CPC Class Codes: H04L 51/00 User-to-user messaging in packet-switching networks, transmitted according to store-and-forward or real-time protocols, e.g. e-mail
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 63/0464 using hop-by-hop encryption, i.e. wherein an intermediate entity decrypts the information and re-encrypts it before forwarding it
• CPC Class Codes: H04L 63/104 Grouping of entities
• CPC Class Codes: H04L 9/0825 using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates
• CPC Class Codes: H04L 9/0833 involving conference or group key network architectures or network communication protocols for key management in group communication in a packet data network H04L63/065

Abstract

One embodiment of the present invention provides a system for sending an encrypted message through a distribution list exploder in order to forward the encrypted message to recipients on a distribution list. The system operates by encrypting the message at a sender using a message key to form an encrypted message. The system also encrypts the message key with a group public key to form an encrypted message key. The group public key is associated with a group private key to form a public key-private key pair associated with a group of valid recipients for the message. Next, the system sends the encrypted message and the encrypted message key to the distribution list exploder, and the distribution list exploder forwards the encrypted message to a plurality of recipients specified in the distribution list. After receiving the encrypted message and the encrypted message key, the recipient decrypts the encrypted message key to restore the message key. Next, the recipient decrypts the encrypted message using the message key to restore the message. In a variation on the above embodiment, the recipient decrypts the encrypted message key by sending the encrypted message key from the recipient to a group server, which holds the group private key. The group server decrypts the encrypted message key using the group private key to restore the message key, and returns the message key to the recipient in a secure manner.

Claims

1. A method for sending a message that is encrypted through a distribution list exploder that forwards the message to recipients on a distribution list, comprising:

encrypting the message at a sender using a message key to form an encrypted message, the message key being randomly selected for the message;

encrypting the message key with a group public key to form an encrypted message key, the group public key being associated with a group private key to form a public key-private key pair associated with a group of valid recipients for the message, wherein neither the sender nor the recipients on the distribution list need to know the group private-key to decrypt the encrypted message-key;

sending the encrypted message and the encrypted message key to the distribution list exploder, the distribution list exploder being configured to forward the encrypted message to a plurality of recipients specified in the distribution list;

forwarding the encrypted message and the encrypted message key from the distribution list exploder to the plurality of recipients;

receiving the encrypted message and the encrypted message key at a recipient from the plurality of recipients;

sending the encrypted message key from the recipient to a group server, the group server possessing the group private key;

decrypting the encrypted message key at the group server using the group private key to restore the message key;

communicating the message key to the recipient in a secure manner;

decrypting the encrypted message at the recipient using the message key to restore the message;

wherein the distribution list exploder forwards the encrypted message and the encrypted message key without communicating with the group server;

whereby causing the recipient to contact the group server directly to decrypt the encrypted message key relieves the distribution list exploder of the burden of communicating with the group server to decrypt the encrypted message key.

2. A method for sending a message that is encrypted through a distribution list exploder that forwards the message to recipients on a distribution list, comprising:

encrypting the message at a sender using a message key to form an encrypted message;

encrypting the message key with a group public key to form an encrypted message key, the group public key being associated with a group private key to form a public key-private key pair associated with a group of valid recipients for the message, wherein neither the sender nor the recipients on the distribution list need to know the group private-key to decrypt the encrypted message-key; and

sending the encrypted message and the encrypted message key to the distribution list exploder, the distribution list exploder being configured to forward the encrypted message to a plurality of recipients specified in the distribution list;

wherein the distribution list exploder forwards the encrypted message and the encrypted message key without communicating with a group server;

whereby causing the recipient to contact a group server directly to decrypt the encrypted message key relieves the distribution list exploder of the burden of communicating with the group server to decrypt the encrypted message key.

3. The method of claim 2, further comprising:

sending the encrypted message key from the distribution list exploder to a group server, the group server possessing the group private key;

decrypting the encrypted message key at the group server using the group private key to restore the message key;

encrypting the message key with a secret key to form a second encrypted message key, the secret key being known to the group of valid recipients for the message;

wherein encrypting the message key with the secret key involves using a symmetric encryption mechanism so that the second encrypted message key can be decrypted using the secret key;

sending the second encrypted message key from the group server to the distribution list exploder; and

forwarding the encrypted message and the second encrypted message key from the distribution list exploder to the plurality of recipients.

4. The method claim 3, further comprising:

decrypting the encrypted message key at a recipient from the plurality of recipients using the secret key to restore the message key; and

decrypting the encrypted message with the message key to restore the message at the recipient.

5. The method of claim 2, further comprising:

decrypting the encrypted message key at the distribution list exploder using the group private key to restore the message key;

encrypting the message key with a secret key to form a second encrypted message key, the secret key being known to the group of valid recipients for the message;

wherein encrypting the message key with the secret key involves using a symmetric encryption mechanism so that the second encrypted message key can be decrypted using the secret key; and

sending the encrypted message and the second encrypted message key from the distribution list exploder to the plurality of recipients.

6. A computer readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for sending a message that is encrypted through a distribution list exploder that forwards the message to recipients on a distribution list, comprising:

encrypting the message at a sender using a message key to form an encrypted message;

encrypting the message key with a group public key to form an encrypted message key, the group public key being associated with a group private key to form a public key-private key pair associated with a group of valid recipients for the message, wherein neither the sender nor the recipients on the distribution list need to know the group private-key to decrypt the encrypted message-key; and

sending the encrypted message and the encrypted message key to the distribution list exploder, the distribution list exploder being configured to forward the encrypted message to a plurality of recipients specified in the distribution list;

wherein the distribution list exploder forwards the encrypted message and the encrypted message key without communicating with a group server;

whereby causing the recipient to contact a group server directly to decrypt the encrypted message key relieves the distribution list exploder of the burden of communicating with the group server to decrypt the encrypted message key.

7. An apparatus that facilitates sending a message that is encrypted through a distribution list exploder that forwards the message to recipients on a distribution list, comprising:

an encryption mechanism, that is configured to,

encrypt the message using a message key to form an encrypted message, and to

encrypt the message key with a group public key to form an encrypted message key, the group public key being associated with a group private key to form a public key-private key pair associated with a group of valid recipients for the message, wherein neither the sender nor the recipients on the distribution list need to know the group private-key to decrypt the encrypted message-key; and

a sending mechanism that is configured to send the encrypted message and the encrypted message key to the distribution list exploder, the distribution list exploder being configured to forward the encrypted message to a plurality of recipients specified in the distribution list;

wherein the distribution list exploder forwards the encrypted message and the encrypted message key without communicating with a group server;

whereby causing the recipient to contact a group server directly to decrypt the encrypted message key relieves the distribution list exploder of the burden of communicating with the group server to decrypt the encrypted message key.

8. The apparatus of claim 7, further comprising:

a second sending mechanism that is configured to send the encrypted message key from the distribution list exploder to a group server, the group server possessing the group private key;

a decryption mechanism within the group server that is configured to decrypt the encrypted message key using the group private key to restore the message key;

a second encryption mechanism within the group server that is configured to encrypt the message key with a secret key to form a second encrypted message key, the secret key being known to the group of valid recipients for the message;

wherein the second encryption mechanism includes a symmetric encryption mechanism so that the second encrypted message key can be decrypted using the secret key;

a third sending mechanism within the group server that is configured to send the second encrypted message key to the distribution list exploder; and

a distribution mechanism within the distribution list exploder that is configured to forward the encrypted message and the second encrypted message key to the plurality of recipients.

9. A method for receiving a message that is encrypted through a distribution list exploder that forwards the message to recipients on a distribution list, comprising:

receiving an encrypted message and an encrypted message key from the distribution list exploder at a recipient;

wherein the encrypted message contains the message that is encrypted using a message key;

wherein the encrypted message key contains the message key that is encrypted using a group public key, the group public key being associated with a group private key to form a public key-private key pair associated with a group of valid recipients for the message, wherein neither the sender nor the recipients on the distribution list need to know the group private-key to decrypt the encrypted message-key;

sending the encrypted message key from the recipient to a group server, the group server possessing the group private key;

allowing the group server to decrypt the encrypted message key using the group private key to restore the message key; and

receiving the message key from the group server in a secure manner;

decrypting the encrypted message key at the recipient to restore the message key; and

decrypting the encrypted message at the recipient using the message key to restore the message;

wherein the distribution list exploder forwards the encrypted message and the encrypted message key without communicating with a group server;

whereby causing the recipient to contact the group server directly to decrypt the encrypted message key relieves the distribution list exploder of the burden of communicating with the group server to decrypt the encrypted message key.

10. The method of claim 9, wherein receiving the message key from the group server in the secure manner comprises:

allowing the group server to encrypt the message key using a recipient public key belonging to the recipient to form a second encrypted message key, the recipient public key being associated with a recipient private key to form a public key-private key pair associated with the recipient;

receiving the second encrypted message key from the group server; and

decrypting the second encrypted message key with the recipient private key to restore the message key.

11. The method of claim 9, wherein receiving the message key from the group server in the secure manner comprises:

authenticating the recipient to the group server;

allowing the group server to verify that the recipient is a member of the group of valid recipients for the message; and

receiving the message key from the group server at the recipient using a secure protocol.

12. The method of claim 11, wherein the secure protocol includes one of, the transport layer security (TLS) protocol and the secure sockets layer (SSL) protocol.

13. The method of claim 9, wherein receiving the message key from the group server in the secure manner comprises:

making a request from the recipient to a certificate server for a certificate, the certificate including a certificate public key, the certificate public key being associated with a certificate private key to form a public key-private key pair;

receiving the certificate from the certificate server only if the recipient is a member of the group of valid recipients for the message;

sending the certificate from the recipient to the group server;

allowing the group server to encrypt the message key with the certificate public key to form a second encrypted message key;

receiving the second encrypted message key at the recipient; and

decrypting the second encrypted message key with the certificate private key to restore the message key.

14. The method of claim 9, wherein receiving the message key from the group server in the secure manner comprises:

allowing the group server to encrypt the message key using a group secret key to form a second encrypted message key, the group secret key being a symmetric key known to the group of valid recipients;

receiving the second encrypted message key at the recipient; and

decrypting the second encrypted message key with the group secret key to restore the message key.