# US 10,311,243 B2 · Method and apparatus for secure communication

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- Number: US 10,311,243 B2
- Document ID: US10311243B2
- Status: Granted
- Kind: B2
- Application number: 14/208,683
- Filed: 2014-03-13
- Published: 2016-06-02
- Granted: 2019-06-04
- Earliest claimed: 2013-03-14
- Assignees: Massachusetts Institute of Technology; National University of Ireland Maynooth
- Applicants: Massachusetts Institute of Technology; National University of Ireland Maynooth
- Inventors: Flavio du Pin Calmon; Muriel Medard; Linda M. Zeger; Mark M. Christiansen; Kenneth R. Duffy
- Web page: https://patentgrep.com/patent/US10311243B2

## CPC

- G06F 21/6209: {to a single file or object, e.g. in a secure envelope, encrypted and accessed using a key, or with access control rules appended to the object itself}
- H04L 9/065: {Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3}
- H04L 63/0435: {wherein the sending and receiving network entities apply symmetric encryption, i.e. same key used for encryption and decryption (cryptographic mechanisms or cryptographic arrangements for symmetric key encryption H04L9/06)}
- H03M 13/1102: {Codes on graphs and decoding on graphs, e.g. low-density parity check [LDPC] codes}
- H03M 13/1515: {Reed-Solomon codes}
- H04L 2209/30: Compression, e.g. Merkle-Damgard construction
- H04L 2209/34: Encoding or coding, e.g. Huffman coding or error correction
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)

## Abstract

Secrecy scheme systems and associated methods using list source codes for enabling secure communications in communications networks are provided herein. Additionally, improved information-theoretic metrics for characterizing and optimizing said secrecy scheme systems and associated methods are provided herein. One method of secure communication comprises receiving a data file at a first location, encoding the data file using a list source code to generate an encoded file, encrypting a select portion of the data file using a key to generate an encrypted file, and transmitting the encoded file and the encrypted file to an end user at a destination location, wherein the encoded file cannot be decoded at the destination location until the encrypted file has been received and decrypted by the end user, wherein the end user possesses the key.

## Claims

### Claim 1

A method of secure communication, the method implemented within a transmitting device having one or more circuits at a first location, the method comprising:
encoding an input data file at the first location using a list source code to generate an encoded data file, wherein using the list source code includes selecting a size of a list of the list source code to tune a desired level of secrecy;
encrypting a select portion of the encoded data file using a key to generate an encrypted data file, wherein the size of the select portion of the encoded data file to be encrypted is used to tune to the desired level of secrecy such that the encoded data file cannot be decoded at the destination location until the encrypted data file has been received and decrypted by a receiving device possessing the key.

### Claim 2 (depends on 1)

The method of claim 1, wherein encrypting a select portion of the encoded data file can occur either before, during, or after transmission of the encoded data file.

### Claim 3 (depends on 1)

The method of claim 1, further comprising: transmitting the key to the destination location either before, during, or after transmission of the encoded data file to the destination location.

### Claim 4 (depends on 1)

The method of claim 1, wherein if the key is compromised during the transmission of the encoded data file, only the transmission of the encrypted data file needs to be aborted.

### Claim 5 (depends on 4)

The method of claim 4, wherein security of the method is not compromised if the transmission of the encoded data file is not aborted.

### Claim 6 (depends on 1)

The method of claim 1, wherein encoding the input data file using a list source code includes encoding the input data file with a linear code that spreads uncertainty over all symbols of the input data file such that an eavesdropper cannot infer any information concerning any sets of k symbols of the input data file.

### Claim 7 (depends on 6)

The method of claim 6, wherein encoding the input data file with a linear code comprises encoding the input data file using a code for which any linear combination of codewords is also a codeword.

### Claim 8 (depends on 6)

The method of claim 6, wherein encoding the input data file with a linear code comprises encoding the input data file using Reed Solomon or low-density parity-check (LDPC).

### Claim 9 (depends on 1)

The method of claim 1, wherein the list source code is a code that compresses a source sequence below its entropy rate.

### Claim 10 (depends on 1)

The method of claim 1, wherein the method is applied as an additional layer of security to an underlying encryption scheme.

### Claim 11 (depends on 1)

The method of claim 1, wherein the method is tunable to a desired level of secrecy, wherein size of the key is dependent upon the desired level of secrecy.

### Claim 12 (depends on 1)

The method of claim 1, wherein the destination location is a remote location.

### Claim 13 (depends on 1)

The method of claim 1, wherein the destination location is the same as the first location.

### Claim 14 (depends on 1)

The method of claim 1, wherein a portion of the encoded data file is transmitted before the encrypted data file and the key are transmitted to the receiving device.

### Claim 15 (depends on 1)

The method of claim 1, wherein the method is used to perform content pre-caching in a network, wherein the encoded data file is distributed and cached within the network and cannot be decoded/decrypted until both the encrypted portion of the encoded data file and the key are received.

### Claim 16

A transmitting system for secure communications comprising:
an encoder operable to encode an input data file at a first location using a list source code to generate an encoded data file, wherein using the list source code includes selecting a size of a list of the list source code to tune a desired level of secrecy;
an encryption circuit operable to encrypt a select portion of the encoded data file using a key to generate an encrypted data file, wherein the size of the select portion of the encoded data file to be encrypted is used to tune to the desired level of secrecy such that the encoded data file cannot be decoded at a destination location until the encrypted data file has been received and decrypted by an end user receiving system possessing the key.

### Claim 17 (depends on 16)

The transmitting system of claim 16, wherein:
the encoded data file is an unencrypted encoded data file; and
encoding the input data file using a list source code includes encoding the input data file with a linear code that spreads uncertainty over all symbols of the input data file such that an eavesdropper cannot infer any information concerning any sets of k symbols of the input data file.

### Claim 18 (depends on 16)

The transmitting system of claim 16, wherein the encrypted data file is an encoded encrypted data file.

### Claim 19

A receiving system comprising:
a receiver operable to receive, at a destination location, one or more of an encoded data file, an encrypted data file, or a key from a first location;
a decryption circuit coupled to the receiver and operable to decrypt the encrypted data file using a key to generate a decrypted data file, wherein the size of the decrypted data file is used to tune to a desired level of secrecy;
a decoder circuit coupled to one or more of the decryption circuit and the receiver and operable to decode one or more of the encoded data file and the decrypted data file using a list source code to generate an output data file, wherein a size of a list of the list source code is used to tune the desired level of secrecy.

### Claim 20 (depends on 19)

The receiving system of claim 19, wherein:
the encoded data file is an unencrypted encoded data file; and
the list source code spreads uncertainty over all symbols of the encoded and encrypted data files such that an eavesdropper cannot infer any information concerning any sets of k symbols of the encoded and encrypted data file.

### Claim 21 (depends on 19)

The receiving system of claim 19, wherein the encrypted data file is an encoded encrypted data file.

### Claim 22 (depends on 19)

The receiving system of claim 19, wherein the output data file comprises a list of potential data files.

### Claim 23 (depends on 22)

The receiving system of claim 22, wherein the decoder circuit is further operable to determine an input data file from the list of potential data files, wherein the input data file is representative of the encoded data file in combination with the encrypted data file.