Indirect public-key encryption

• US 6,779,111 B1
• Filed: 05/10/1999
• Issued: 08/17/2004
• Est. Priority Date: 05/10/1999
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Gehrmann, Christian, Barriga, Luis
• Primary Examiner(s): Wright, Norman M.
• Application Number:
  US09/309,151
• Time in Patent Office: 1,926 Days
• Field of Search: 380/259, 380/267, 380/28, 380/29, 380/30, 713/189, 713/150, 713/162, 713/161, 713/168, 713/170
• US Class Current: 713/171
• CPC Class Codes: H04L 2209/04 Masking or blinding
• CPC Class Codes: H04L 2209/08 Randomization, e.g. dummy operations or using noise
• CPC Class Codes: H04L 2209/76 Proxy, i.e. using intermediary entity to perform cryptographic operations network architectures or network communication protocols using hop-by-hop encryption H04L63/0464
• CPC Class Codes: H04L 9/302 involving the integer factorization problem, e.g. RSA or quadratic sieve [QS] schemes

Abstract

A system and method for encrypting data communications between a client and server utilizes an untrusted proxy server to perform computationally expensive encryption calculations which would otherwise be performed by the client. Prior to transmitting the data message to the proxy server, the client masks the data message such that the data message is indecipherable to the untrusted proxy. The untrusted proxy performs the computationally expensive encryption calculations prior to transmitting the data message to the intended receiver.

Claims

1. A method of transmitting information from a first device to a second device, said method comprising the steps of:

generating, by said first device, a random value (X);

computing, by said first device, a second value (Y) based on the random value and a public key associated with said second device;

masking, by said first device, the information (M) using the random value (X);

transmitting the masked information (Z) and the second value (Y) from said first device to an untrusted proxy;

generating, by said untrusted proxy, an encrypted form (M′

) of the information (M) based on the masked information (Z), and the second value (Y), received from said first device; and

transmitting said encypted information (M′

) from said untrusted proxy to said second device.

2. The method of claim 1, wherein the masking step comprises multiplying the information by the random value.

3. The method recited in claim 1, wherein said random number (X) conforms to Xε

[0, n−

1].

4. The method recited in claim 1, wherein said public key is identified by [e, n], and wherein said second value (Y) is identified by Y=X^e mod n.

5. The method recited in claim 1, wherein the stop of masking said information (M) using said random number (X) conforms to Z=(X·

M) mod n, where M is the information and Z is the masked information.

6. The method recited in claim 1, wherein said step of encrypting, by said untrusted proxy, the information (M) based on the masked information (Z) and the second value (Y) comprises the step of computing (Z^e mod n)/Y=((X·

M)^e mod n)/(X^e mod n)=M^e mod n=M′

, where M′

is the enrypted information.